Forests, nitrogen and albedo, a very interesting trio indeed

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Borghetti M

2009-01-01

Full Text Available A short comment is made on a recent paper (Ollinger et al. 2008 which shows that forest ecosystem carbon uptake in temperate and boreal forests is directly related to canopy nitrogen concentration and that both carbon uptake capacity and canopy nitrogen concentration are positively correlated with shortwave surface albedo measured with broad-band satellite sensors.

Improved Canopy Sensor-based Corn Nitrogen Recommendations Using Auxiliary Information

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The nitrogen (N) supplying capacity of the soil available to support corn (Zea mays L.) production can be highly variable both among and within fields. Thus, the amount of N fertilizer applied should be site-specific and also climate-sensitive. In recent years, canopy reflectance sensing has been in...

Estimating Canopy Nitrogen Concentration in Sugarcane Using Field Imaging Spectroscopy

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Marc Souris

2012-06-01

Full Text Available The retrieval of nutrient concentration in sugarcane through hyperspectral remote sensing is widely known to be affected by canopy architecture. The goal of this research was to develop an estimation model that could explain the nitrogen variations in sugarcane with combined cultivars. Reflectance spectra were measured over the sugarcane canopy using a field spectroradiometer. The models were calibrated by a vegetation index and multiple linear regression. The original reflectance was transformed into a First-Derivative Spectrum (FDS and two absorption features. The results indicated that the sensitive spectral wavelengths for quantifying nitrogen content existed mainly in the visible, red edge and far near-infrared regions of the electromagnetic spectrum. Normalized Differential Index (NDI based on FDS_(750/700 and Ratio Spectral Index (RVI based on FDS_(724/700 are best suited for characterizing the nitrogen concentration. The modified estimation model, generated by the Stepwise Multiple Linear Regression (SMLR technique from FDS centered at 410, 426, 720, 754, and 1,216 nm, yielded the highest correlation coefficient value of 0.86 and Root Mean Square Error of the Estimate (RMSE value of 0.033%N (n = 90 with nitrogen concentration in sugarcane. The results of this research demonstrated that the estimation model developed by SMLR yielded a higher correlation coefficient with nitrogen content than the model computed by narrow vegetation indices. The strong correlation between measured and estimated nitrogen concentration indicated that the methods proposed in this study could be used for the reliable diagnosis of nitrogen quantity in sugarcane. Finally, the success of the field spectroscopy used for estimating the nutrient quality of sugarcane allowed an additional experiment using the polar orbiting hyperspectral data for the timely determination of crop nutrient status in rangelands without any requirement of prior

Remote sensing of canopy nitrogen at regional scale in Mediterranean forests using the spaceborne MERIS Terrestrial Chlorophyll Index

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Loozen, Yasmina; Rebel, Karin T.; Karssenberg, Derek; Wassen, Martin J.; Sardans, Jordi; Peñuelas, Josep; De Jong, Steven M.

2018-05-01

Canopy nitrogen (N) concentration and content are linked to several vegetation processes. Therefore, canopy N concentration is a state variable in global vegetation models with coupled carbon (C) and N cycles. While there are ample C data available to constrain the models, widespread N data are lacking. Remotely sensed vegetation indices have been used to detect canopy N concentration and canopy N content at the local scale in grasslands and forests. Vegetation indices could be a valuable tool to detect canopy N concentration and canopy N content at larger scale. In this paper, we conducted a regional case-study analysis to investigate the relationship between the Medium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI) time series from European Space Agency (ESA) Envisat satellite at 1 km spatial resolution and both canopy N concentration (%N) and canopy N content (N g m-2, of ground area) from a Mediterranean forest inventory in the region of Catalonia, in the northeast of Spain. The relationships between the datasets were studied after resampling both datasets to lower spatial resolutions (20, 15, 10 and 5 km) and at the original spatial resolution of 1 km. The results at higher spatial resolution (1 km) yielded significant log-linear relationships between MTCI and both canopy N concentration and content: r2 = 0.32 and r2 = 0.17, respectively. We also investigated these relationships per plant functional type. While the relationship between MTCI and canopy N concentration was strongest for deciduous broadleaf and mixed plots (r2 = 0.24 and r2 = 0.44, respectively), the relationship between MTCI and canopy N content was strongest for evergreen needleleaf trees (r2 = 0.19). At the species level, canopy N concentration was strongly related to MTCI for European beech plots (r2 = 0.69). These results present a new perspective on the application of MTCI time series for canopy N detection.

Exploring canopy structure and function as a potential mechanism of sustain carbon sequestration in aging forests

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Fotis, A. T.; Curtis, P.; Ricart, R.

2013-12-01

The notion that old-growth forests reach carbon neutrality has recently been challenged, but the mechanisms responsible for continued productivity have remained elusive. Increases in canopy structural complexity, defined by high horizontal and vertical variability in leaf distribution (rugosity), has been proposed as a mechanism for sustained high rates of above ground net primary production (ANPPw) in forests up to ~170 years by enhancing light use efficiency (LUE) and nitrogen use efficiency (NUE). However, a detailed understanding of how rugosity affects resource distribution within and among trees leading to greater LUE and NUE is not known. We propose that leaves in high rugosity plots receive greater photosynthetic photon flux density (PPFD) than leaves in low rugosity plots, causing shifts from shade- to sun- adapted leaves into deeper portions of the canopy, which is thought to increase the photosynthetic capacity of individuals and lead to higher carbon assimilation in forests. The goal of this research was to: 1) quantify different canopy structural characteristics using a portable canopy LiDAR (PCL) and; 2) assess how these structural characteristics affect resource distribution and subsequent changes in leaf morphological, physiological and biochemical traits in three broadleaf species (e.g., Acer rubrum, Quercus rubra and Fagus grandifolia) and one conifer species (e.g., Pinus strobus) at different levels in the canopy in plots with similar leaf are index (LAI) but highly contrasting rugosity levels. We found that gap fraction had a strong positive correlation with rugosity. High rugosity plots had a bimodal distribution of LAI that was concentrated at the top and bottom of the canopy with an open midstory (between 10-50% of total canopy height) whereas low rugosity plots had a more even distribution of leaves. Leaf mass per area (LMA) of all broadleaved species had a strong positive correlation with cumulative gap fraction (P. strobus had a relatively

Cotton responses to simulated insect damage: radiation-use efficiency, canopy architecture and leaf nitrogen content as affected by loss of reproductive organs

International Nuclear Information System (INIS)

Sadras, V.O.

1996-01-01

Key cotton pests feed preferentially on reproductive organs which are normally shed after injury. Loss of reproductive organs in cotton may decrease the rate of leaf nitrogen depletion associated with fruit growth and increase nitrogen uptake and reduction by extending the period of root and leaf growth compared with undamaged plants. Higher levels of leaf nitrogen resulting from more assimilation and less depletion could increase the photosynthetic capacity of damaged crops in relation to undamaged controls. To test this hypothesis, radiation-use efficiency (RUE = g dry matter per MJ of photosynthetically active radiation intercepted by the canopy) of crops in which flowerbuds and young fruits were manually removed was compared with that of undamaged controls. Removal of fruiting structures did not affect RUE when cotton was grown at low nitrogen supply and high plant density. In contrast, under high nitrogen supply and low plant density, fruit removal increased seasonal RUE by 20–27% compared to controls. Whole canopy measurements, however, failed to detect the expected variations in foliar nitrogen due to damage. Differences in RUE between damaged and undamaged canopies were in part associated with changes in plant and canopy structure (viz. internode number and length, canopy height, branch angle) that modified light distribution within the canopy. These structural responses and their influence on canopy light penetration and photosynthesis are synthetised in coefficients of light extinction (k) that were 10 to 30% smaller in damaged crops than in controls and in a positive correlation between RUE−1 and k for crops grown under favourable conditions (i.e. high nitrogen, low density). Changes in plant structure and their effects on canopy architecture and RUE should be considered in the analysis of cotton growth after damage by insects that induce abscission of reproductive organs. (author)

Chlorophyll Can Be Reduced in Crop Canopies with Little Penalty to Photosynthesis1[OPEN

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Drewry, Darren T.; VanLoocke, Andy; Cho, Young B.

2018-01-01

The hypothesis that reducing chlorophyll content (Chl) can increase canopy photosynthesis in soybeans was tested using an advanced model of canopy photosynthesis. The relationship among leaf Chl, leaf optical properties, and photosynthetic biochemical capacity was measured in 67 soybean (Glycine max) accessions showing large variation in leaf Chl. These relationships were integrated into a biophysical model of canopy-scale photosynthesis to simulate the intercanopy light environment and carbon assimilation capacity of canopies with wild type, a Chl-deficient mutant (Y11y11), and 67 other mutants spanning the extremes of Chl to quantify the impact of variation in leaf-level Chl on canopy-scale photosynthetic assimilation and identify possible opportunities for improving canopy photosynthesis through Chl reduction. These simulations demonstrate that canopy photosynthesis should not increase with Chl reduction due to increases in leaf reflectance and nonoptimal distribution of canopy nitrogen. However, similar rates of canopy photosynthesis can be maintained with a 9% savings in leaf nitrogen resulting from decreased Chl. Additionally, analysis of these simulations indicate that the inability of Chl reductions to increase photosynthesis arises primarily from the connection between Chl and leaf reflectance and secondarily from the mismatch between the vertical distribution of leaf nitrogen and the light absorption profile. These simulations suggest that future work should explore the possibility of using reduced Chl to improve canopy performance by adapting the distribution of the “saved” nitrogen within the canopy to take greater advantage of the more deeply penetrating light. PMID:29061904

Effect of Vertical Canopy Architecture on Transpiration, Thermoregulation and Carbon Assimilation

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Tirtha Banerjee

2018-04-01

Full Text Available Quantifying the impact of natural and anthropogenic disturbances such as deforestation, forest fires and vegetation thinning among others on net ecosystem—atmosphere exchanges of carbon dioxide, water vapor and heat—is an important aspect in the context of modeling global carbon, water and energy cycles. The absence of canopy architectural variation in horizontal and vertical directions is a major source of uncertainty in current climate models attempting to address these issues. This manuscript demonstrates the importance of considering the vertical distribution of foliage density by coupling a leaf level plant biophysics model with analytical solutions of wind flow and light attenuation in a horizontally homogeneous canopy. It is demonstrated that plant physiological response in terms of carbon assimilation, transpiration and canopy surface temperature can be widely different for two canopies with the same leaf area index (LAI but different leaf area density distributions, under several conditions of wind speed, light availability, soil moisture availability and atmospheric evaporative demand.

A specific PFT and sub-canopy structure for simulating oil palm in the Community Land Model

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Fan, Y.; Knohl, A.; Roupsard, O.; Bernoux, M.; LE Maire, G.; Panferov, O.; Kotowska, M.; Meijide, A.

2015-12-01

Towards an effort to quantify the effects of rainforests to oil palm conversion on land-atmosphere carbon, water and energy fluxes, a specific plant functional type (PFT) and sub-canopy structure are developed for simulating oil palm within the Community Land Model (CLM4.5). Current global land surface models only simulate annual crops beside natural vegetation. In this study, a multilayer oil palm subroutine is developed in CLM4.5 for simulating oil palm's phenology and carbon and nitrogen allocation. The oil palm has monopodial morphology and sequential phenology of around 40 stacked phytomers, each carrying a large leaf and a fruit bunch, forming a natural multilayer canopy. A sub-canopy phenological and physiological parameterization is thus introduced, so that multiple phytomer components develop simultaneously but according to their different phenological steps (growth, yield and senescence) at different canopy layers. This specific multilayer structure was proved useful for simulating canopy development in terms of leaf area index (LAI) and fruit yield in terms of carbon and nitrogen outputs in Jambi, Sumatra (Fan et al. 2015). The study supports that species-specific traits, such as palm's monopodial morphology and sequential phenology, are necessary representations in terrestrial biosphere models in order to accurately simulate vegetation dynamics and feedbacks to climate. Further, oil palm's multilayer structure allows adding all canopy-level calculations of radiation, photosynthesis, stomatal conductance and respiration, beside phenology, also to the sub-canopy level, so as to eliminate scale mismatch problem among different processes. A series of adaptations are made to the CLM model. Initial results show that the adapted multilayer radiative transfer scheme and the explicit represention of oil palm's canopy structure improve on simulating photosynthesis-light response curve. The explicit photosynthesis and dynamic leaf nitrogen calculations per canopy

Nitrogen vertical distribution by canopy reflectance spectrum in winter wheat

International Nuclear Information System (INIS)

Huang, W J; Yang, Q Y; Peng, D L; Huang, L S; Zhang, D Y; Yang, G J

2014-01-01

Nitrogen is a key factor for plant photosynthesis, ecosystem productivity and leaf respiration. Under the condition of nitrogen deficiency, the crop shows the nitrogen deficiency symptoms in the bottom leaves, while excessive nitrogen will affect the upper layer leaves first. Thus, timely measurement of vertical distribution of foliage nitrogen content is critical for growth diagnosis, crop management and reducing environmental impact. This study presents a method using bi-directional reflectance difference function (BRDF) data to invert foliage nitrogen vertical distribution. We developed upper-layer nitrogen inversion index (ULNI), middle-layer nitrogen inversion index (MLNI) and bottom-layer nitrogen inversion index (BLNI) to reflect foliage nitrogen inversion at upper layer, middle layer and bottom layer, respectively. Both ULNI and MLNI were made by the value of the ratio of Modified Chlorophyll Absorption Ration Index to the second Modified Triangular Vegetation Index (MCARI/MTVI2) referred to as canopy nitrogen inversion index (CNII) in this study at ±40° and ±50°, and at ±30° and ±40° view angles, respectively. The BLNI was composed by the value of nitrogen reflectance index (NRI) at ±20° and ±30° view angles. These results suggest that it is feasible to measure foliage nitrogen vertical-layer distribution in a large scale by remote sensing

Fusing corn nitrogen recommendation tools for an improved canopy reflectance sensor performance

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Nitrogen (N) rate recommendation tools are utilized to help producers maximize corn grain yield production. Many of these tools provide recommendations at field scales but often fail when corn N requirements are variable across the field. Canopy reflectance sensors are capable of capturing within-fi...

Evapotranspiration and water use efficiency in relation to climate and canopy nitrogen in U.S. forests

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Guerrieri, Rossella; Lepine, Lucie; Asbjornsen, Heidi; Xiao, Jingfeng; Ollinger, Scott V.

2016-10-01

Understanding relations among forest carbon (C) uptake and water use is critical for predicting forest-climate interactions. Although the basic properties of tree-water relations have long been known, our understanding of broader-scale patterns is limited by several factors including (1) incomplete understanding of drivers of change in coupled C and water fluxes and water use efficiency (WUE), (2) difficulty in reconciling WUE estimates obtained at different scales, and (3) uncertainty in how evapotranspiration (ET) and WUE vary with other important resources such as nitrogen (N). To address these issues, we examined ET, gross primary production (GPP), and WUE at 11 AmeriFlux sites across North America. Our analysis spanned leaf and ecosystem scales and included foliar δ13C, δ18O, and %N measurements; eddy covariance estimates of GPP and ET; and remotely sensed estimates of canopy %N. We used flux data to derive ecosystem WUE (WUEe) and foliar δ13C to infer intrinsic WUE. We found that GPP, ET, and WUEe scaled with canopy %N, even when environmental variables were considered, and discuss the implications of these relationships for forest-atmosphere-climate interactions. We observed opposing patterns of WUE at leaf and ecosystem scales and examined uncertainties to help explain these opposing patterns. Nevertheless, significant relationship between C isotope-derived ci/ca and GPP indicates that δ13C can be an effective predictor of forest GPP. Finally, we show that incorporating species functional traits—wood anatomy, hydraulic strategy, and foliar %N—into a conceptual model improved the interpretation of Δ13C and δ18O vis-à-vis leaf to canopy water-carbon fluxes.

Nitrogen isotope variations in camphor (Cinnamomum Camphora) leaves of different ages in upper and lower canopies as an indicator of atmospheric nitrogen sources

Energy Technology Data Exchange (ETDEWEB)

Xiao Huayun, E-mail: xiaohuayun@vip.skleg.c [State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, No. 46, Guanshui Road, Guiyang 550002 (China); Wu Lianghong; Zhu Renguo; Wang Yanli; Liu Congqiang [State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, No. 46, Guanshui Road, Guiyang 550002 (China)

2011-02-15

Nitrogen isotopic composition of new, middle-aged and old camphor leaves in upper and lower canopies has been determined in a living area, near a motorway and near an industrial area (Jiangan Chemical Fertilizer Plant). We found that at sites near roads, more positive {delta}{sup 15}N values were observed in the camphor leaves, especially in old leaves of upper canopies, and {Delta}{delta}{sup 15}N = {delta}{sup 15}N{sub upper} - {delta}{sup 15}N{sub lower} > 0, while those near the industrial area had more negative {delta}{sup 15}N values and {Delta}{delta}{sup 15}N < 0. These could be explained by two isotopically different atmospheric N sources: greater uptake from isotopically heavy pools of atmospheric NO{sub x} by old leaves in upper canopies at sites adjacent to roads, and greater uptake of {sup 15}N-depleted NH{sub y} in atmospheric deposition by leaves at sites near the industrial area. This study presents novel evidence that {sup 15}N natural abundance of camphor leaves can be used as a robust indicator of atmospheric N sources. - Research highlights: Camphor leaves showed high {delta}{sup 15}N values near roads and low values near the industrial area. The {delta}{sup 15}N values of camphor leaves near roads increased with time of exposure. The {delta}{sup 15}N values of camphor leaves near the industrial area decreased with time of exposure. More positive foliage {delta}{sup 15}N values were found in the upper canopies near roads. Near the industrial area, the upper canopies showed more negative foliage {delta}{sup 15}N values. - Nitrogen isotope in camphor leaves indicating atmospheric nitrogen sources.

Seasonal and within-canopy variation in shoot-scale resource-use efficiency trade-offs in a Norway spruce stand.

Science.gov (United States)

Tarvainen, Lasse; Räntfors, Mats; Wallin, Göran

2015-11-01

Previous leaf-scale studies of carbon assimilation describe short-term resource-use efficiency (RUE) trade-offs where high use efficiency of one resource requires low RUE of another. However, varying resource availabilities may cause long-term RUE trade-offs to differ from the short-term patterns. This may have important implications for understanding canopy-scale resource use and allocation. We used continuous gas exchange measurements collected at five levels within a Norway spruce, Picea abies (L.) karst., canopy over 3 years to assess seasonal differences in the interactions between shoot-scale resource availability (light, water and nitrogen), net photosynthesis (An ) and the use efficiencies of light (LUE), water (WUE) and nitrogen (NUE) for carbon assimilation. The continuous data set was used to develop and evaluate multiple regression models for predicting monthly shoot-scale An . These models showed that shoot-scale An was strongly dependent on light availability and was generally well described with simple one- or two-parameter models. WUE peaked in spring, NUE in summer and LUE in autumn. However, the relative importance of LUE for carbon assimilation increased with canopy depth at all times. Our results suggest that accounting for seasonal and within-canopy trade-offs may be important for RUE-based modelling of canopy carbon uptake. © 2015 John Wiley & Sons Ltd.

NITROGEN CONTENT AND DRY-MATTER DIGESTIBILITY OF GUINEA AND SABI GRASSES AS INFLUENCED BY TREE LEGUME CANOPY

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Andi Lagaligo Amar

2012-08-01

Full Text Available A research study was undertaken to study the grass layer across a mini landscape dominated by tree legume Albizia lebbeck to explore the nutritional differences of two introduced grasses, guinea grass (Panicum maximum and sabi grass (Urochloa mosambicensis, paying particular attention to the presence or absence of tree legume canopy of Albizia lebbeck. The two grass species showed a tendency to replace the native spear grass (Heteropogon contortus; their dominance was more or less complete under tree canopies but was increasing in open areas between trees. Nutritional differences were examined by nitrogen concentration and dry matter digestibility. For comparison, Heteropogon contortus, a native species only found in the open, was included in the nutritional determination using the same methods as the guinea and sabi grasses. The quality parameters of the pasture species were statistically compared (LSD, P=0.05. The quality of herbage was different between the species. Urochloa mosambicensis was better than Panicum maximum. In the open, sabi grass has higher N content (0.62% than guinea grass (0.55%, but they were similar when grown under the canopy (0.69% and 0.72%, respectively. Sabi grass has consistently higher dry matter digestibility (41.39% and 36.83%, respectively under the canopy and in the open, than guinea grass (27.78% and 24.77%. These two species are much higher in both N concentration and dry matter digestibility than the native spear grass. The native species has contained 0.28% N, and 17.65% digestible dry matter. The feeding values of herbage were influenced by the canopy factor. Both guinea and sabi grasses have better quality when grown under the tree canopies than in between canopies. Nitrogen concentration and dry matter digestibility of the guinea grass under canopy were, 0.72% and 27.78%, respectively, significantly higher than those from the open area, 0.55% and 24.77%. Similarly, herbage of sabi grass under canopy has 0

Estimation of In-canopy Flux Distributions of Reactive Nitrogen and Sulfur within a Mixed Hardwood Forest in Southern Appalachia

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Wu, Z.; Walker, J. T.; Chen, X.; Oishi, A. C.; Duman, T.

2017-12-01

Estimating the source/sink distribution and vertical fluxes of air pollutants within and above forested canopies is critical for understanding biological, physical, and chemical processes influencing the soil-vegetation-atmosphere exchange. The vertical source-sink profiles of reactive nitrogen and sulfur were examined using multiple inverse modeling methods in a mixed hardwood forest in the southern Appalachian Mountains where the ecosystem is highly sensitive to loads of pollutant from atmospheric depositions. Measurements of the vertical concentration profiles of ammonia (NH3), nitric acid (HNO3), sulfur dioxide (SO2), and ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-) in PM2.5 were measured during five study periods between May 2015 and August 2016. The mean concentration of NH3 decreased with height in the upper canopy and increased below the understory toward the forest floor, indicating that the canopy was a sink for NH3 but the forest floor was a source. All other species exhibited patterns of monotonically decreasing concentration from above the canopy to the forest floor. Using the measured concentration profiles, we simulated the within-canopy flow fields and estimated the vertical source-sink flux profiles using three inverse approaches: a Eulerian high-order closure model (EUL), a Lagrangian localized near-field (LNF) model, and a new full Lagrangian stochastic model (LSM). The models were evaluated using the within- and above-canopy eddy covariance flux measurements of heat, CO2 and H2O. Differences between models were analyzed and the flux profiles were used to investigate the origin and fate of reactive nitrogen and sulfur compounds within the canopy. The knowledge gained in this study will benefit the development of soil-vegetation-atmosphere models capable of partitioning canopy-scale deposition of nitrogen and sulfur to specific ecosystem compartments.

Estimating foliar biochemistry from hyperspectral data in mixed forest canopy

DEFF Research Database (Denmark)

Huber Gharib, Silvia; Kneubühler, Mathias; Psomas, Achilleas

2008-01-01

data to estimate the foliar concentration of nitrogen, carbon and water in three mixed forest canopies in Switzerland. With multiple linear regression models, continuum-removed and normalized HyMap spectra were related to foliar biochemistry on an individual tree level. The six spectral wavebands used...

Relationships between net photosynthesis and foliar nitrogen concentrations in a loblobby pine forest ecosystem grown in elevated atmospheric carbon dioxide

International Nuclear Information System (INIS)

Springer, C. J.; Thomas, R. B.; Delucia, E. H.

2005-01-01

The effects of elevated carbon dioxide concentration on the relationship between light-saturated net photosynthesis and area-based foliar nitrogen concentration in the canopy of a loblobby pine forest at the Duke Forest FACE experiment was examined. Two overstory and four understory tree species were examined at their growth carbon dioxide concentrations during the early summer and late summer of 1999, 2001 and 2002. Light-saturated net photosynthesis and foliar nitrogen relationship were compared to determine if the stimulatory effects of elevated carbon dioxide on net photosynthesis had declined. Results at all three sample times showed no difference in either the slopes, or in the y-intercepts of the net photosynthesis-foliar nitrogen relationship when measured at common carbon dioxide concentrations. Net photosynthesis was also unaffected by growth in elevated carbon dioxide, indicating that these overstory and understory trees continued to show strong stimulation of photosynthesis by elevated carbon dioxide. 46 refs., 6 tabs., 3 figs

Evaluating Uncertainties in Sap Flux Scaled Estimates of Forest Transpiration, Canopy Conductance and Photosynthesis

Science.gov (United States)

Ward, E. J.; Bell, D. M.; Clark, J. S.; Kim, H.; Oren, R.

2009-12-01

Thermal dissipation probes (TDPs) are a common method for estimating forest transpiration and canopy conductance from sap flux rates in trees, but their implementation is plagued by uncertainties arising from missing data and variability in the diameter and canopy position of trees, as well as sapwood conductivity within individual trees. Uncertainties in estimates of canopy conductance also translate into uncertainties in carbon assimilation in models such as the Canopy Conductance Constrained Carbon Assimilation (4CA) model that combine physiological and environmental data to estimate photosynthetic rates. We developed a method to propagate these uncertainties in the scaling and imputation of TDP data to estimates of canopy transpiration and conductance using a state-space Jarvis-type conductance model in a hierarchical Bayesian framework. This presentation will focus on the impact of these uncertainties on estimates of water and carbon fluxes using 4CA and data from the Duke Free Air Carbon Enrichment (FACE) project, which incorporates both elevated carbon dioxide and soil nitrogen treatments. We will also address the response of canopy conductance to vapor pressure deficit, incident radiation and soil moisture, as well as the effect of treatment-related stand structure differences in scaling TDP measurements. Preliminary results indicate that in 2006, a year of normal precipitation (1127 mm), canopy transpiration increased in elevated carbon dioxide ~8% on a ground area basis. In 2007, a year with a pronounced drought (800 mm precipitation), this increase was only present in the combined carbon dioxide and fertilization treatment. The seasonal dynamics of water and carbon fluxes will be discussed in detail.

High-Resolution Forest Canopy Height Estimation in an African Blue Carbon Ecosystem

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Lagomasino, David; Fatoyinbo, Temilola; Lee, Seung-Kuk; Simard, Marc

2015-01-01

Mangrove forests are one of the most productive and carbon dense ecosystems that are only found at tidally inundated coastal areas. Forest canopy height is an important measure for modeling carbon and biomass dynamics, as well as land cover change. By taking advantage of the flat terrain and dense canopy cover, the present study derived digital surface models (DSMs) using stereophotogrammetric techniques on high-resolution spaceborne imagery (HRSI) for southern Mozambique. A mean-weighted ground surface elevation factor was subtracted from the HRSI DSM to accurately estimate the canopy height in mangrove forests in southern Mozambique. The mean and H100 tree height measured in both the field and with the digital canopy model provided the most accurate results with a vertical error of 1.18-1.84 m, respectively. Distinct patterns were identified in the HRSI canopy height map that could not be discerned from coarse shuttle radar topography mission canopy maps even though the mode and distribution of canopy heights were similar over the same area. Through further investigation, HRSI DSMs have the potential of providing a new type of three-dimensional dataset that could serve as calibration/validation data for other DSMs generated from spaceborne datasets with much larger global coverage. HSRI DSMs could be used in lieu of Lidar acquisitions for canopy height and forest biomass estimation, and be combined with passive optical data to improve land cover classifications.

Combining multiple isotopes and metagenomic to delineate the role of tree canopy nitrification in European forests along nitrogen deposition and climate gradients

Science.gov (United States)

Guerrieri, R.; Avila, A.; Barceló, A.; Elustondo, D.; Hellstein, S.; Magnani, F.; Mattana, S.; Matteucci, G.; Merilä, P.; Michalski, G. M.; Nicolas, M.; Vanguelova, E.; Verstraeten, A.; Waldner, P.; Watanabe, M.; Penuelas, J.; Mencuccini, M.

2017-12-01

Forest canopies influence our climate through carbon, water and energy exchanges with the atmosphere. However, less investigated is whether and how tree canopies change the chemical composition of precipitation, with important implications on forest nutrient cycling. Recently, we provided for the first time isotopic evidence that biological nitrification in tree canopies was responsible for significant changes in the amount of nitrate from rainfall to throughfall across two UK forests at high nitrogen (N) deposition [1]. This finding strongly suggested that bacteria and/or Archaea species of the phyllosphere are responsible for transforming atmospheric N before it reaches the soil. Despite microbial epiphytes representing an important component of tree canopies, attention has been mostly directed to their role as pathogens, while we still do not know whether and how they affect nutrient cycling. Our study aims to 1) characterize microbial communities harboured in tree canopies for two of the most dominant species in Europe (Fagus sylvatica L. and Pinus sylvestris L.) using metagenomic techniques, 2) quantify the functional genes related to nitrification but also to denitrification and N fixation, and 3) estimate the contribution of NO3 derived from biological canopy nitrification vs. atmospheric NO3 input by using δ15N, δ18O and δ17O of NO3in forest water. We considered i) twelve sites included in the EU ICP long term intensive forest monitoring network, chosen along a climate and nitrogen deposition gradient, spanning from Fennoscandia to the Mediterranean and ii) a manipulation experiment where N mist treatments were carried out either to the soil or over tree canopies. We will present preliminary results regarding microbial diversity in the phyllosphere, water (rainfall and throughfall) and soil samples over the gradient. Furthermore, we will report differences between the two investigated tree species for the phyllosphere core microbiome in terms of relative

Remote Sensing of Vegetation Nitrogen Content for Spatially Explicit Carbon and Water Cycle Estimation

Science.gov (United States)

Zhang, Y. L.; Miller, J. R.; Chen, J. M.

2009-05-01

Foliage nitrogen concentration is a determinant of photosynthetic capacity of leaves, thereby an important input to ecological models for estimating terrestrial carbon and water budgets. Recently, spectrally continuous airborne hyperspectral remote sensing imagery has proven to be useful for retrieving an important related parameter, total chlorophyll content at both leaf and canopy scales. Thus remote sensing of vegetation biochemical parameters has promising potential for improving the prediction of global carbon and water balance patterns. In this research, we explored the feasibility of estimating leaf nitrogen content using hyperspectral remote sensing data for spatially explicit estimation of carbon and water budgets. Multi-year measurements of leaf biochemical contents of seven major boreal forest species were carried out in northeastern Ontario, Canada. The variation of leaf chlorophyll and nitrogen content in response to various growth conditions, and the relationship between them,were investigated. Despite differences in plant type (deciduous and evergreen), leaf age, stand growth conditions and developmental stages, leaf nitrogen content was strongly correlated with leaf chlorophyll content on a mass basis during the active growing season (r2=0.78). With this general correlation, leaf nitrogen content was estimated from leaf chlorophyll content at an accuracy of RMSE=2.2 mg/g, equivalent to 20.5% of the average measured leaf nitrogen content. Based on this correlation and a hyperspectral remote sensing algorithm for leaf chlorophyll content retrieval, the spatial variation of leaf nitrogen content was inferred from the airborne hyperspectral remote sensing imagery acquired by Compact Airborne Spectrographic Imager (CASI). A process-based ecological model Boreal Ecosystem Productivity Simulator (BEPS) was used for estimating terrestrial carbon and water budgets. In contrast to the scenario with leaf nitrogen content assigned as a constant value without

Temporal dynamics of light and nitrogen vertical distributions in canopies of sunflower, kenaf and cynara

NARCIS (Netherlands)

Archontoulis, S.V.; Vos, J.; Yin, X.; Bastiaans, L.; Danalatos, N.G.; Struik, P.C.

2011-01-01

To enhance eco-physiological and modelling studies, we quantified vertical distributions of light and nitrogen in canopies of three Mediterranean bio-energy crops: sunflower (Helianthus annuus), kenaf (Hibiscus cannabinus) and cynara (Cynara cardunculus). Field crops were grown with and without

Effects of nitrogen nutrition on the growth, yield and reflectance characteristics of corn canopies. [Purdue Agronomy Farm, Indiana

Science.gov (United States)

Bauer, M. E. (Principal Investigator); Walburg, G.; Daughtry, C. S. T.

1981-01-01

Spectral and agronomic measurements were collected from corn (Zea mays L.) canopies under four nitrogen treatment levels (0, 67, 134, and 202 kg/ha) on 11 dates during 1978 and 12 dates during 1979. Data were analyzed to determine the relationship between the spectral responses of canopies and their argonomic characteristics as well as the spectral separability of the four treatments. Red reflectance was increased, while the near infrared reflectance was decreased for canopies under nitrogen deprivation. Spectral differences between treatments were seen throughout each growing season. The near infrared/red reflectance ratio increased spectral treatment differences over those shown by single band reflectance measures. Of the spectral variables examined, the near infrared/red reflectance ratio most effectively separated the treatments. Differences in spectral response between treatments were attributed to varying soil cover, leaf area index, and leaf pigmentation values, all of which changed with N treatment.

Glasshouse seedling δ13C and canopy δ13C of 8-year-old hoop pine families grown in south-east Queensland in relation to canopy δ18O, nitrogen concentration and tree growth

International Nuclear Information System (INIS)

Prasolova, N.V.; Saffigna, P.G.; Farquhar, G.D.

1999-01-01

Full text: Carbon isotope composition (δ l3 C) in C 3 plants has been theoretically and empirically linked to plant water-use efficiency (WUE). The plant δ 13 C has been suggested as an early selection criterion in plant breeding. The δ 13 C and nitrogen concentration (N mass ) of branchlet tissue for inner and outer upper canopy positions were assessed for 8-year-old hoop pine (Araucaria cunninghamii Ait.ex D.Don) trees from 23 half-sib families grown in 5 blocks of a progeny test in south-east Queensland, and for glasshouse seedlings. Tree height was positively related to N mass in branchlets of the 2 canopy positions, indicating that tree growth was limited by nitrogen deficiency. Our data indicated that water supply was also a growth-limiting factor in the hoop pine plantation of the study-area. There were considerable variations in δ 13 C and N mass between families and blocks in the field (with a heritability estimate of 0.73 for branchlet δ 13 C from the inner canopy position). Significant variation in δ 13 C was observed between positions and families of the glasshouse seedlings (with a heritability estimate of 0.66). There was also a significant difference in N mass between the 2 sampling positions in the field. The δ 13 C was positively related to N mass for the branchlets of the upper outer crown (r=0.62, p 13 C (r: 0.28-0.41, p l3 C of the 2 canopy positions for all the 115 trees sampled. There was no significant correlation between δ 13 C values for 2 seedling canopy positions at age 18 months, possibly due to restricted rooting conditions in small pots, leading to greater stomatal closure in upper canopy, which was also reflected in more positive δ 13 C. Significant correlation existed between seedling δ 13 C of upper canopy position at age 8 months and low canopy position at age 18 months. This, together with field data, demonstrated the sensitivity and reliability of δ 13 C as an indicator of plant growth environment. Strong correlation

Impact of Vertical Canopy Position on Leaf Spectral Properties and Traits across Multiple Species

Directory of Open Access Journals (Sweden)

Tawanda W. Gara

2018-02-01

Full Text Available Understanding the vertical pattern of leaf traits across plant canopies provide critical information on plant physiology, ecosystem functioning and structure and vegetation response to climate change. However, the impact of vertical canopy position on leaf spectral properties and subsequently leaf traits across the entire spectrum for multiple species is poorly understood. In this study, we examined the ability of leaf optical properties to track variability in leaf traits across the vertical canopy profile using Partial Least Square Discriminatory Analysis (PLS-DA. Leaf spectral measurements together with leaf traits (nitrogen, carbon, chlorophyll, equivalent water thickness and specific leaf area were studied at three vertical canopy positions along the plant stem: lower, middle and upper. We observed that foliar nitrogen (N, chlorophyll (Cab, carbon (C, and equivalent water thickness (EWT were higher in the upper canopy leaves compared with lower shaded leaves, while specific leaf area (SLA increased from upper to lower canopy leaves. We found that leaf spectral reflectance significantly (P ≤ 0.05 shifted to longer wavelengths in the ‘red edge’ spectrum (685–701 nm in the order of lower > middle > upper for the pooled dataset. We report that spectral bands that are influential in the discrimination of leaf samples into the three groups of canopy position, based on the PLS-DA variable importance projection (VIP score, match with wavelength regions of foliar traits observed to vary across the canopy vertical profile. This observation demonstrated that both leaf traits and leaf reflectance co-vary across the vertical canopy profile in multiple species. We conclude that canopy vertical position has a significant impact on leaf spectral properties of an individual plant’s traits, and this finding holds for multiple species. These findings have important implications on field sampling protocols, upscaling leaf traits to canopy level

Modeling canopy-level productivity: is the "big-leaf" simplification acceptable?

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Sprintsin, M.; Chen, J. M.

2009-05-01

The "big-leaf" approach to calculating the carbon balance of plant canopies assumes that canopy carbon fluxes have the same relative responses to the environment as any single unshaded leaf in the upper canopy. Widely used light use efficiency models are essentially simplified versions of the big-leaf model. Despite its wide acceptance, subsequent developments in the modeling of leaf photosynthesis and measurements of canopy physiology have brought into question the assumptions behind this approach showing that big leaf approximation is inadequate for simulating canopy photosynthesis because of the additional leaf internal control on carbon assimilation and because of the non-linear response of photosynthesis on leaf nitrogen and absorbed light, and changes in leaf microenvironment with canopy depth. To avoid this problem a sunlit/shaded leaf separation approach, within which the vegetation is treated as two big leaves under different illumination conditions, is gradually replacing the "big-leaf" strategy, for applications at local and regional scales. Such separation is now widely accepted as a more accurate and physiologically based approach for modeling canopy photosynthesis. Here we compare both strategies for Gross Primary Production (GPP) modeling using the Boreal Ecosystem Productivity Simulator (BEPS) at local (tower footprint) scale for different land cover types spread over North America: two broadleaf forests (Harvard, Massachusetts and Missouri Ozark, Missouri); two coniferous forests (Howland, Maine and Old Black Spruce, Saskatchewan); Lost Creek shrubland site (Wisconsin) and Mer Bleue petland (Ontario). BEPS calculates carbon fixation by scaling Farquhar's leaf biochemical model up to canopy level with stomatal conductance estimated by a modified version of the Ball-Woodrow-Berry model. The "big-leaf" approach was parameterized using derived leaf level parameters scaled up to canopy level by means of Leaf Area Index. The influence of sunlit

Integrating soil and weather information into canopy sensor algorithms for improved corn nitrogen rate recommendation

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Corn production can be often limited by the loss of nitrogen (N) due to leaching, volatilization and denitrification. The use of canopy sensors for making in-season N fertilizer applications has been proven effective in matching plant N requirements with periods of rapid N uptake (V7-V11), reducing ...

The impact of modifying photosystem antenna size on canopy photosynthetic efficiency-Development of a new canopy photosynthesis model scaling from metabolism to canopy level processes.

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Song, Qingfeng; Wang, Yu; Qu, Mingnan; Ort, Donald R; Zhu, Xin-Guang

2017-12-01

Canopy photosynthesis (A c ) describes photosynthesis of an entire crop field and the daily and seasonal integrals of A c positively correlate with daily and seasonal biomass production. Much effort in crop breeding has focused on improving canopy architecture and hence light distribution inside the canopy. Here, we develop a new integrated canopy photosynthesis model including canopy architecture, a ray tracing algorithm, and C 3 photosynthetic metabolism to explore the option of manipulating leaf chlorophyll concentration ([Chl]) for greater A c and nitrogen use efficiency (NUE). Model simulation results show that (a) efficiency of photosystem II increased when [Chl] was decreased by decreasing antenna size and (b) the light received by leaves at the bottom layers increased when [Chl] throughout the canopy was decreased. Furthermore, the modelling revealed a modest ~3% increase in A c and an ~14% in NUE was accompanied when [Chl] reduced by 60%. However, if the leaf nitrogen conserved by this decrease in leaf [Chl] were to be optimally allocated to other components of photosynthesis, both A c and NUE can be increased by over 30%. Optimizing [Chl] coupled with strategic reinvestment of conserved nitrogen is shown to have the potential to support substantial increases in A c , biomass production, and crop yields. © 2017 The Authors Plant, Cell & Environment Published by John Wiley & Sons Ltd.

Canopy uptake of atmospheric N deposition at a conifer forest: part I -canopy N budget, photosynthetic efficiency and net ecosystem exchange

International Nuclear Information System (INIS)

Sievering, H.; Tomaszewski, T.; Torizzo, J.

2007-01-01

Global carbon cycle assessments of anthropogenic nitrogen (N) deposition influences on carbon sequestration often assume enhanced sequestration results. This assumption was evaluated at a Rocky Mountains spruce-fir forest. Forest canopy N uptake (CNU) of atmospheric N deposition was estimated by combining event wet and throughfall N fluxes with gradient measured HNO 3 and NH 3 as well as inferred (NO x and particulate N) dry fluxes. Approximately 80% of the growing-season 3 kg N/ha total deposition is retained in canopy foliage and branches. This CNU constitutes ∼1/3 of canopy growing season new N supply at this conifer forest site. Daytime net ecosystem exchange (NEE) significantly (P = 0.006) and negatively (CO 2 uptake) correlated with CNU. Multiple regression indicates ∼20% of daytime NEE may be attributed to CNU (P < 0.02); more than soil water content. A wet deposition N-amendment study (Tomaszewski and Sievering), at canopy spruce branches, increased their growing-season CNU by 40-50% above ambient. Fluorometry and gas exchange results show N-amended spruce branches had greater photosynthetic efficiency and higher carboxylation rates than control and untreated branches. N-amended branches had 25% less photoinhibition, with a 5-9% greater proportion of foliar-N-in-Rubisco. The combined results provide, partly, a mechanistic explanation for the NEE dependence on CNU

Nitrogen dynamics across silvicultural canopy gaps in young forests of western Oregon

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Thiel, A.L.; Perakis, S.S.

2009-01-01

Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. The effect of gap creation on available nitrogen (N) is of concern to managers because N is often a limiting nutrient in Pacific Northwest forests. We investigated patterns of N availability in the forest floor and upper mineral soil (0-10 cm) across 6-8-year-old silvicultural canopy gaps in three 50-70-year-old Douglas-fir forests spanning a wide range of soil N capital in the Coast Range and Cascade Mountains of western Oregon. We used extractable ammonium (NH4+) and nitrate (NO3-) pools, net N mineralization and nitrification rates, and NH4+ and NO3- ion exchange resin (IER) concentrations to quantify N availability along north-south transects run through the centers of 0.4 and 0.1 ha gaps. In addition, we measured several factors known to influence N availability, including litterfall, moisture, temperature, and decomposition rates. In general, gap-forest differences in N availability were more pronounced in the mineral soil than in the forest floor. Mineral soil extractable NH4+ and NO3- pools, net N mineralization and nitrification rates, and NH4+ and NO3- IER concentrations were all significantly elevated in gaps relative to adjacent forest, and in several cases exhibited significantly greater spatial variability in gaps than forest. Nitrogen availability along the edges of gaps more often resembled levels in the adjacent forest than in gap centers. For the majority of response variables, there were no significant differences between northern and southern transect positions, nor between 0.4 and 0.1 ha gaps. Forest floor and mineral soil gravimetric percent moisture and temperature showed few differences along transects, while litterfall carbon (C) inputs and litterfall C:N ratios in gaps were significantly lower than in the adjacent forest. Reciprocal transfer incubations of

Measurements of canopy chemistry with 1992 AVIRIS data at Blackhawk Island and Harvard Forest

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Martin, Mary E.; Aber, John D.

1993-01-01

The research described in this paper was designed to determine if high spectral resolution imaging spectrometer data can be used to measure the chemical composition of forest foliage, specifically nitrogen and lignin concentration. Information about the chemical composition of forest canopies can be used to determine nutrient cycling rates and carbon balances in forest ecosystems. This paper will describe the results relating data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) to field measured canopy chemistry at Blackhawk Island, WI and Harvard Forest, MA.

Effect of 3D nitrogen, dry mass per area and local irradiance on canopy photosynthesis within leaves of contrasted heterogeneous maize crops.

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Drouet, J-L; Bonhomme, R

2004-06-01

Nitrogen partitioning within stands has been described fairly comprehensively, especially for C(3) plants in dense stands where the horizontal heterogeneity of foliage distribution is relatively small. Nitrogen has been shown to be distributed vertically and in parallel to light, maximizing carbon assimilation and stand productivity. Conversely, row crops such as maize (C(4) plants) are characterized by strong horizontal heterogeneity of foliage distribution, and a three-dimensional (3D) approach is required to investigate the combined effect of spatial distribution of nitrogen and light on canopy photosynthesis. The 3D geometry of maize canopies was modelled with varying densities and at different developmental stages using plant digitizing under field conditions. For lamina parts, photosynthesis was measured and nitrogen content per unit area (N(a)) was described from analysis of nitrogen content per unit mass (N(m)) and dry mass per unit area (M(a)). Hyperbolic relationships between photosynthesis at irradiance saturation (P(max)) and N(a) were established as well as a linear relationship between dark respiration (R(d)) and N(a), whereas quantum efficiency (alpha) was found to be independent of N(a). N(m), M(a) and N(a) were shown to change over time vertically (i.e. between laminae), which has been largely reported previously, and horizontally (i.e. within laminae), which has scarcely been described previously. Even if M(a) played a major role in N(a), a strong relationship between N(a) and M(a) could not be demonstrated, whereas several previous studies have found that N(a) was essentially related to M(a) rather than N(m). From simulations of radiative exchange using a 3D volume-based approach and lamina photosynthesis using a hyperbola, it was shown that real patterns of N(a) partitioning could increase daily crop photosynthesis by up to 8 % compared with uniform patterns of N(a), especially for the earliest stages of stand development.

On the use of phloem sap δ13C to estimate canopy carbon discrimination

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Rascher, Katherine; Máguas, Cristina; Werner, Christiane

2010-05-01

Although the carbon stable isotope composition (d13C) of bulk leaf material is a good integrative parameter of photosynthetic discrimination and can be used as a reliable ecological index of plant functioning; it is not a good tracer of short-term changes in photosynthetic discrimination. In contrast, d13C of phloem sap is potentially useful as an indicator of short-term changes in canopy photosynthetic discrimination. However, recent research indicates that d13C signatures may be substantially altered by metabolic processes downstream of initial leaf-level carbon fixation (e.g. post-photosynthetic fractionation). Accordingly, before phloem sap d13C can be used as a proxy for canopy level carbon discrimination an understanding of factors influencing the degree and magnitude of post-photosynthetic fractionation and how these vary between species is of paramount importance. In this study, we measured the d13C signature along the basipetal transport pathway in two co-occurring tree species in the field - an understory invasive exotic legume, Acacia longifolia, and a native pine, Pinus pinaster. We measured d13C of bulk leaf and leaf water soluble organic matter (WSOM), phloem sap sampled at two points along the plant axis and leaf and root dark respiration. In general, species differences in photosynthetic discrimination resulted in more enriched d13C values in the water-conserving P. pinaster relative to the water-spending A. longifolia. Post-photosynthetic fractionation led to differences in d13C of carbon pools along the plant axis with progressively more depleted d13C from the canopy to the trunk (~6.5 per mil depletion in A. longifolia and ~0.8per mil depletion in P. pinaster). Leaf and root respiration, d13C, were consistently enriched relative to putative substrates. We hypothesize that the pronounced enrichment of leaf respired CO2 relative to leaf WSOM may have left behind relatively depleted carbon to be loaded into the phloem resulting in d13C depletion

Evidence for substantial forestry canopy processing of nitrogen deposition using isotopic tracer experiments in low deposition conditions

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Ferraretto, Daniele; Heal, Kate

2017-04-01

Temperate forest ecosystems are significant sinks for nitrogen deposition (Ndep) yielding benefits such as protection of waterbodies from eutrophication and enhanced sequestration of atmospheric CO2. Previous studies have shown evidence of biological nitrification and Ndep processing and retention in forest canopies. However, this was reported only at sites with high environmental or experimentally enhanced rates of Ndep (˜18 kg N ha-1 y-1) and has not yet been demonstrated in low Ndep environments. We have used bulk field hydrochemical measurements and labelled isotopic experiments to assess canopy processing in a lower Ndep environment (˜7 kg N ha-1 year-1) at a Sitka spruce plantation in Perthshire, Scotland, representing the dominant tree species (24%) in woodlands in Great Britain. Analysis of 4.5 years of measured N fluxes in rainfall (RF) and fogwater onto the canopy and throughfall (TF) and stemflow (SF) below the canopy suggests strong transformation and uptake of Ndep in the forest canopy. Annual canopy Ndep uptake was ˜4.7 kg N ha-1 year-1, representing 60-76% of annual Ndep. To validate these plot-scale results and track N uptake within the forest canopy in different seasons, double 15N-labelled NH4NO3 (98%) solution was sprayed in summer and winter onto the canopy of three trees at the measurement site. RF, TF and SF samples have been collected and analysed for 15NH4 and 15NO3. Comparing the amount of labelled N recovered under the sample trees with the measured δ15N signal is expected to provide further evidence of the role of forest canopies in actively processing and retaining atmospheric N deposition.

Net primary production and canopy nitrogen in a temperate forest landscape: an analysis using imaging spectroscopy, modeling and field data

Science.gov (United States)

Scott V. Ollinger; Marie-Louise Smith

2005-01-01

Understanding spatial patterns of net primary production (NPP) is central to the study of terrestrial ecosystems, but efforts are frequently hampered by a lack of spatial information regarding factors such as nitrogen availability and site history. Here, we examined the degree to which canopy nitrogen can serve as an indicator of patterns of NPP at the Bartlett...

Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4

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Bonan, Gordon B.; Oleson, Keith W.; Fisher, Rosie A.; Lasslop, Gitta; Reichstein, Markus

2012-06-01

The Community Land Model version 4 overestimates gross primary production (GPP) compared with estimates from FLUXNET eddy covariance towers. The revised model of Bonan et al. (2011) is consistent with FLUXNET, but values for the leaf-level photosynthetic parameterVcmaxthat yield realistic GPP at the canopy-scale are lower than observed in the global synthesis of Kattge et al. (2009), except for tropical broadleaf evergreen trees. We investigate this discrepancy betweenVcmaxand canopy fluxes. A multilayer model with explicit calculation of light absorption and photosynthesis for sunlit and shaded leaves at depths in the canopy gives insight to the scale mismatch between leaf and canopy. We evaluate the model with light-response curves at individual FLUXNET towers and with empirically upscaled annual GPP. Biases in the multilayer canopy with observedVcmaxare similar, or improved, compared with the standard two-leaf canopy and its lowVcmax, though the Amazon is an exception. The difference relates to light absorption by shaded leaves in the two-leaf canopy, and resulting higher photosynthesis when the canopy scaling parameterKn is low, but observationally constrained. Larger Kndecreases shaded leaf photosynthesis and reduces the difference between the two-leaf and multilayer canopies. The low modelVcmaxis diagnosed from nitrogen reduction of GPP in simulations with carbon-nitrogen biogeochemistry. Our results show that the imposed nitrogen reduction compensates for deficiency in the two-leaf canopy that produces high GPP. Leaf trait databases (Vcmax), within-canopy profiles of photosynthetic capacity (Kn), tower fluxes, and empirically upscaled fields provide important complementary information for model evaluation.

A leaf gas exchange model that accounts for intra-canopy variability by considering leaf nitrogen content and local acclimation to radiation in grapevine (Vitis vinifera L.).

Science.gov (United States)

Prieto, Jorge A; Louarn, Gaëtan; Perez Peña, Jorge; Ojeda, Hernán; Simonneau, Thierry; Lebon, Eric

2012-07-01

Understanding the distribution of gas exchange within a plant is a prerequisite for scaling up from leaves to canopies. We evaluated whether leaf traits were reliable predictors of the effects of leaf ageing and leaf irradiance on leaf photosynthetic capacity (V(cmax) , J(max) ) in field-grown vines (Vitis vinifera L). Simultaneously, we measured gas exchange, leaf mass per area (LMA) and nitrogen content (N(m) ) of leaves at different positions within the canopy and at different phenological stages. Daily mean leaf irradiance cumulated over 10 d (PPFD(10) ) was obtained by 3D modelling of the canopy structure. N(m) decreased over the season in parallel to leaf ageing while LMA was mainly affected by leaf position. PPFD(10) explained 66, 28 and 73% of the variation of LMA, N(m) and nitrogen content per area (N(a) ), respectively. Nitrogen content per unit area (N(a) = LMA × N(m) ) was the best predictor of the intra-canopy variability of leaf photosynthetic capacity. Finally, we developed a classical photosynthesis-stomatal conductance submodel and by introducing N(a) as an input, the model accurately simulated the daily pattern of gas exchange for leaves at different positions in the canopy and at different phenological stages during the season. © 2012 Blackwell Publishing Ltd.

Remote estimation of nitrogen and chlorophyll contents in maize at leaf and canopy levels

Science.gov (United States)

Schlemmer, M.; Gitelson, A.; Schepers, J.; Ferguson, R.; Peng, Y.; Shanahan, J.; Rundquist, D.

2013-12-01

Leaf and canopy nitrogen (N) status relates strongly to leaf and canopy chlorophyll (Chl) content. Remote sensing is a tool that has the potential to assess N content at leaf, plant, field, regional and global scales. In this study, remote sensing techniques were applied to estimate N and Chl contents of irrigated maize (Zea mays L.) fertilized at five N rates. Leaf N and Chl contents were determined using the red-edge chlorophyll index with R2 of 0.74 and 0.94, respectively. Results showed that at the canopy level, Chl and N contents can be accurately retrieved using green and red-edge Chl indices using near infrared (780-800 nm) and either green (540-560 nm) or red-edge (730-750 nm) spectral bands. Spectral bands that were found optimal for Chl and N estimations coincide well with the red-edge band of the MSI sensor onboard the near future Sentinel-2 satellite. The coefficient of determination for the relationships between the red-edge chlorophyll index, simulated in Sentinel-2 bands, and Chl and N content was 0.90 and 0.87, respectively.

Estimating Canopy Dark Respiration for Crop Models

Science.gov (United States)

Monje Mejia, Oscar Alberto

2014-01-01

Crop production is obtained from accurate estimates of daily carbon gain.Canopy gross photosynthesis (Pgross) can be estimated from biochemical models of photosynthesis using sun and shaded leaf portions and the amount of intercepted photosyntheticallyactive radiation (PAR).In turn, canopy daily net carbon gain can be estimated from canopy daily gross photosynthesis when canopy dark respiration (Rd) is known.

Is nitrogen the next carbon?

Science.gov (United States)

Battye, William; Aneja, Viney P.; Schlesinger, William H.

2017-09-01

Just as carbon fueled the Industrial Revolution, nitrogen has fueled an Agricultural Revolution. The use of synthetic nitrogen fertilizers and the cultivation of nitrogen-fixing crops both expanded exponentially during the last century, with most of the increase occurring after 1960. As a result, the current flux of reactive, or fixed, nitrogen compounds to the biosphere due to human activities is roughly equivalent to the total flux of fixed nitrogen from all natural sources, both on land masses and in the world's oceans. Natural fluxes of fixed nitrogen are subject to very large uncertainties, but anthropogenic production of reactive nitrogen has increased almost fivefold in the last 60 years, and this rapid increase in anthropogenic fixed nitrogen has removed any uncertainty on the relative importance of anthropogenic fluxes to the natural budget. The increased use of nitrogen has been critical for increased crop yields and protein production needed to keep pace with the growing world population. However, similar to carbon, the release of fixed nitrogen into the natural environment is linked to adverse consequences at local, regional, and global scales. Anthropogenic contributions of fixed nitrogen continue to grow relative to the natural budget, with uncertain consequences.

Nitrogen-doped carbon aerogels for electrical energy storage

Science.gov (United States)

Campbell, Patrick; Montalvo, Elizabeth; Baumann, Theodore F.; Biener, Juergen; Merrill, Matthew; Reed, Eric W.; Worsley, Marcus A.

2017-10-03

Disclosed here is a method for making a nitrogen-doped carbon aerogel, comprising: preparing a reaction mixture comprising formaldehyde, at least one nitrogen-containing resorcinol analog, at least one catalyst, and at least one solvent; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel; and thermally annealing the dry gel to produce the nitrogen-doped carbon aerogel. Also disclosed is a nitrogen-doped carbon aerogel obtained according to the method and a supercapacitor comprising the nitrogen-doped carbon aerogel.

From leaf longevity to canopy seasonality: a carbon optimality phenology model for tropical evergreen forests

Science.gov (United States)

Xu, X.; Medvigy, D.; Wu, J.; Wright, S. J.; Kitajima, K.; Pacala, S. W.

2016-12-01

Tropical evergreen forests play a key role in the global carbon, water and energy cycles. Despite apparent evergreenness, this biome shows strong seasonality in leaf litter and photosynthesis. Recent studies have suggested that this seasonality is not directly related to environmental variability but is dominated by seasonal changes of leaf development and senescence. Meanwhile, current terrestrial biosphere models (TBMs) can not capture this pattern because leaf life cycle is highly underrepresented. One challenge to model this leaf life cycle is the remarkable diversity in leaf longevity, ranging from several weeks to multiple years. Ecologists have proposed models where leaf longevity is regarded as a strategy to optimize carbon gain. However previous optimality models can not be readily integrated into TBMs because (i) there are still large biases in predicted leaf longevity and (ii) it is never tested whether the carbon optimality model can capture the observed seasonality in leaf demography and canopy photosynthesis. In this study, we develop a new carbon optimality model for leaf demography. The novelty of our approach is two-fold. First, we incorporate a mechanistic photosynthesis model that can better estimate leaf carbon gain. Second, we consider the interspecific variations in leaf senescence rate, which strongly influence the modelled optimal carbon gain. We test our model with a leaf trait database for Panamanian evergreen forests. Then, we apply the model at seasonal scale and compare simulated seasonality of leaf litter and canopy photosynthesis with in-situ observations from several Amazonian forest sites. We find that (i) compared with original optimality model, the regression slope between observed and predicted leaf longevity increases from 0.15 to 1.04 in our new model and (ii) that our new model can capture the observed seasonal variations of leaf demography and canopy photosynthesis. Our results suggest that the phenology in tropical evergreen

Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

Science.gov (United States)

Bukata, Andrew R; Kyser, T Kurtis

2007-02-15

Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

Nitrogen deposition's role in determining forest photosynthetic capacity; a FLUXNET synthesis

Science.gov (United States)

Fleischer, K.; Rebel, K.; van der Molen, M.; Erisman, J.; Wassen, M.; Dolman, H.

2011-12-01

There is growing evidence that nitrogen (N) deposition stimulates forest growth, as many forest ecosystems are N-limited. However, the significance of N deposition in determining the strength of the present and future terrestrial carbon sink is strongly debated. We investigated and quantified the effect of N deposition on ecosystem photosynthetic capacity (Amax) with the FLUXNET database, including 80 forest sites, covering the major forest types and climates of the world. The relative effect of climate and N deposition on photosynthesis was assessed with regression models. We found a significant positive correlation of Amax and N deposition for evergreen needleleaf forests in our dataset. We further found indications that foliar N and LAI scale positively with N deposition, reflecting the 2 mechanisms at which N is believed to cause an increase in carbon gain. We can support the hypothesis that foliar N is the principal scaling factor for canopy Amax across all forest types. Deciduous forests are less diverse in terms of climate and nutritional conditions for the included sites and these forests exhibited weak to no correlations with the included climate and N predictor variables. Quantifying the effect of N deposition on photosynthetic rates at the canopy level is an essential step for quantifying its contribution to the terrestrial carbon sink and for predicting vegetation response to N fertilization and global change in the future. The approach shows that eddy-covariance measurements of carbon fluxes at the canopy scale allow us to test hypotheses with respect to the expected nitrogen-photosynthesis relationships at the canopy scale.

Carbon isotope discrimination, ash, and canopy temperature in three wheatgrass species

International Nuclear Information System (INIS)

Frank, A.B.; Ray, I.M.; Berdahl, R.D.; Karn, J.F.

1997-01-01

Soil water is the main factor influencing forage production in the semiarid Northern Great Plains. Developing germplasm that uses limited water more efficiently would benefit forage production for hay and livestock grazing. Development of selection criteria suited to screening large breeding populations for water-use efficiency (WUE) are needed to enhance this effort. This study evaluated carbon isotope discrimination (delta), tissue ash concentration, and canopy temperature of populations of diploid crested wheatgrass (Agropyron cristatum L.), tetraploid crested wheatgrass [A. desertorum (Fisch. ex. Link) Schult.], and western wheatgrass [Pascopyrum smithii (Rybd.) Love] to determine the utility of using ash concentration and canopy temperature as alternative criteria to delta for selecting plants with high WUE. Tissue ash concentration, canopy temperature, and delta were measured on half-sib families from genetically broad-based populations of each species across two field growing seasons. Sufficient genetic variation was present for delta and ash concentration among families within each species to suggest possible use of these traits as criteria for selecting plants with higher WUE. Differences in canopy temperature among families were present only in 1994. Correlations between ash and delta were greatest for tetraploid crested wheatgrass and least for western wheatgrass. Correlation of canopy temperature with delta was significant for tetraploid crested wheatgrass both years and for diploid crested wheatgrass in 1993, but neither year for western wheatgrass. Ash concentration and delta were moderately heritable in all three grass populations, indicating that both traits are under genetic control and could likely be altered through breeding. Using ash and canopy temperature as criteria for selecting plants with greater WUE would provide a relatively low-cost, simple approach to develop cultivars with improved WUE

Nitrogen-doped carbon monolith for alkaline supercapacitors and understanding nitrogen-induced redox transitions.

Science.gov (United States)

Wang, Da-Wei; Li, Feng; Yin, Li-Chang; Lu, Xu; Chen, Zhi-Gang; Gentle, Ian R; Lu, Gao Qing; Cheng, Hui-Ming

2012-04-23

A nitrogen-doped porous carbon monolith was synthesized as a pseudo-capacitive electrode for use in alkaline supercapacitors. Ammonia-assisted carbonization was used to dope the surface with nitrogen heteroatoms in a way that replaced carbon atoms but kept the oxygen content constant. Ammonia treatment expanded the micropore size-distributions and increased the specific surface area from 383 m(2) g(-1) to 679 m(2) g(-1). The nitrogen-containing porous carbon material showed a higher capacitance (246 F g(-1)) in comparison with the nitrogen-free one (186 F g(-1)). Ex situ electrochemical spectroscopy was used to investigate the evolution of the nitrogen-containing functional groups on the surface of the N-doped carbon electrodes in a three-electrode cell. In addition, first-principles calculations were explored regarding the electronic structures of different nitrogen groups to determine their relative redox potentials. We proposed possible redox reaction pathways based on the calculated redox affinity of different groups and surface analysis, which involved the reversible attachment/detachment of hydroxy groups between pyridone and pyridine. The oxidation of nitrogen atoms in pyridine was also suggested as a possible reaction pathway. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon-nitrogen interactions in forest ecosystems

DEFF Research Database (Denmark)

Gundersen, Per; Berg, Bjørn; Currie, W.S.

This report is a summary of the main results from the EU project “Carbon – Nitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C ...

Explaining biomass growth of tropical canopy trees: the importance of sapwood

OpenAIRE

Sande, van der, M.T.; Zuidema, P.A.; Sterck, F.J.

2015-01-01

Tropical forests are important in worldwide carbon (C) storage and sequestration. C sequestration of these forests may especially be determined by the growth of canopy trees. However, the factors driving variation in growth among such large individuals remain largely unclear. We evaluate how crown traits [total leaf area, specific leaf area and leaf nitrogen (N) concentration] and stem traits [sapwood area (SA) and sapwood N concentration] measured for individual trees affect absolute biomass...

Terrestrial nitrogen-carbon cycle interactions at the global scale.

Science.gov (United States)

Zaehle, S

2013-07-05

Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen-carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001-2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr(-1) (1.9 Pg C yr(-1)), of which 10 Tg N yr(-1) (0.2 Pg C yr(-1)) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen-carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr(-1) per 1°C degree climate warming) will add an important long-term climate forcing.

Hierarchically structured, nitrogen-doped carbon membranes

KAUST Repository

Wang, Hong

2017-08-03

The present invention is a structure, method of making and method of use for a novel macroscopic hierarchically structured, nitrogen-doped, nano-porous carbon membrane (HNDCMs) with asymmetric and hierarchical pore architecture that can be produced on a large-scale approach. The unique HNDCM holds great promise as components in separation and advanced carbon devices because they could offer unconventional fluidic transport phenomena on the nanoscale. Overall, the invention set forth herein covers a hierarchically structured, nitrogen-doped carbon membranes and methods of making and using such a membranes.

Seasonal variations of leaf and canopy properties tracked by ground-based NDVI imagery in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Heskel, Mary; Sun, Shucun; Tang, Jianwu

2017-04-28

Changes in plant phenology affect the carbon flux of terrestrial forest ecosystems due to the link between the growing season length and vegetation productivity. Digital camera imagery, which can be acquired frequently, has been used to monitor seasonal and annual changes in forest canopy phenology and track critical phenological events. However, quantitative assessment of the structural and biochemical controls of the phenological patterns in camera images has rarely been done. In this study, we used an NDVI (Normalized Difference Vegetation Index) camera to monitor daily variations of vegetation reflectance at visible and near-infrared (NIR) bands with high spatial and temporal resolutions, and found that the infrared camera based NDVI (camera-NDVI) agreed well with the leaf expansion process that was measured by independent manual observations at Harvard Forest, Massachusetts, USA. We also measured the seasonality of canopy structural (leaf area index, LAI) and biochemical properties (leaf chlorophyll and nitrogen content). We found significant linear relationships between camera-NDVI and leaf chlorophyll concentration, and between camera-NDVI and leaf nitrogen content, though weaker relationships between camera-NDVI and LAI. Therefore, we recommend ground-based camera-NDVI as a powerful tool for long-term, near surface observations to monitor canopy development and to estimate leaf chlorophyll, nitrogen status, and LAI.

Optimising carbon and nitrogen sources for Azotobacter ...

African Journals Online (AJOL)

The present work deals with selecting and optimization of carbon and nitrogen sources for producing biomass from Azotobacter chroococcum. Four carbon sources (glucose, sucrose, manitol and sodium benzoate) and four nitrogen sources (yeast extract, meat extract, NH4Cl and (NH4)2SO4) were evaluated during the first ...

Remarkable activity of nitrogen-doped hollow carbon spheres encapsulated Cu on synthesis of dimethyl carbonate: Role of effective nitrogen

Science.gov (United States)

Li, Haixia; Zhao, Jinxian; Shi, Ruina; Hao, Panpan; Liu, Shusen; Li, Zhong; Ren, Jun

2018-04-01

A critical aspect in the improvement of the catalytic performance of Cu-based catalysts for the synthesis of dimethyl carbonate (DMC) is the development of an appropriate support. In this work, nitrogen-doped hollow carbon spheres (NHCSs), with 240 nm average diameter, 17 nm shell thickness, uniform mesoporous structure and a specific surface area of 611 m2 g-1, were prepared via a two-step Stӧber method. By varying the quantity of nitrogen-containing phenols used in the preparation it has been possible to control the nitrogen content and, consequently, the sphericity of the NHCSs. It was found that perfect spheres were obtained for nitrogen contents below 5.4 wt.%. The catalysts (Cu@NHCSs) were prepared by the hydrothermal impregnation method. The catalytic activity towards DMC synthesis was notably enhanced due to the immobilization effect on Cu particles and the enhanced electron transfer effect exercised by the effective nitrogen species, including pyridinic-N and graphitic-N. When the average size of the copper nanoparticles was 7.4 nm and the nitrogen content was 4.0 wt.%, the values of space-time yield of DMC and of turnover frequency (TOF) reached 1528 mg/(g h) and 11.0 h-1, respectively. The TOF value of Cu@NHCSs was 6 times higher than non-doped Cu@Carbon (2.1 h-1). The present work introduces the potential application of nitrogen-doped carbon materials and presents a novel procedure for the preparation of catalysts for DMC synthesis.

Preparation of nitrogen-doped carbon tubes

Science.gov (United States)

Chung, Hoon Taek; Zelenay, Piotr

2015-12-22

A method for synthesizing nitrogen-doped carbon tubes involves preparing a solution of cyanamide and a suitable transition metal-containing salt in a solvent, evaporating the solvent to form a solid, and pyrolyzing the solid under an inert atmosphere under conditions suitable for the production of nitrogen-doped carbon tubes from the solid. Pyrolyzing for a shorter period of time followed by rapid cooling resulted in a tubes with a narrower average diameter.

The Synthesis of Nitrogen-Doped Multiwalled Carbon Nanotubes ...

African Journals Online (AJOL)

ACVDmethod was used to prepare high-quality nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) using acetonitrile as the nitrogen and carbon source and acetylene as a carbon source over an Fe-Co/CaCO3 catalyst in the temperature range 700–850 °C. This represents a continuation of earlier work in which ...

Spatial Variability Analysis of Within-Field Winter Wheat Nitrogen and Grain Quality Using Canopy Fluorescence Sensor Measurements

Directory of Open Access Journals (Sweden)

Xiaoyu Song

2017-03-01

Full Text Available Wheat grain protein content (GPC is a key component when evaluating wheat nutrition. It is also important to determine wheat GPC before harvest for agricultural and food process enterprises in order to optimize the wheat grading process. Wheat GPC across a field is spatially variable due to the inherent variability of soil properties and position in the landscape. The objectives of this field study were: (i to assess the spatial and temporal variability of wheat nitrogen (N attributes related to the grain quality of winter wheat production through canopy fluorescence sensor measurements; and (ii to examine the influence of spatial variability of soil N and moisture across different growth stages on the wheat grain quality. A geostatistical approach was used to analyze data collected from 110 georeferenced locations. In particular, Ordinary Kriging Analysis (OKA was used to produce maps of wheat GPC, GPC yield, and wheat canopy fluorescence parameters, including simple florescence ratio and Nitrogen Balance Indices (NBI. Soil Nitrate-Nitrogen (NO3-N content and soil Time Domain Reflectometry (TDR value in the study field were also interpolated through the OKA method. The fluorescence parameter maps, soil NO3-N and soil TDR maps obtained from the OKA output were compared with the wheat GPC and GPC yield maps in order to assess their relationships. The results of this study indicate that the NBI spatial variability map in the late stage of wheat growth can be used to distinguish areas that produce higher GPC.

Nitrogen doped silicon-carbon multilayer protective coatings on carbon obtained by TVA method

Science.gov (United States)

Ciupina, Victor; Vasile, Eugeniu; Porosnicu, Corneliu; Lungu, Cristian P.; Vladoiu, Rodica; Jepu, Ionut; Mandes, Aurelia; Dinca, Virginia; Caraiane, Aureliana; Nicolescu, Virginia; Cupsa, Ovidiu; Dinca, Paul; Zaharia, Agripina

2017-08-01

Protective nitrogen doped Si-C multilayer coatings on carbon, used to improve the oxidation resistance of carbon, were obtained by Thermionic Vacuum Arc (TVA) method. The initial carbon layer having a thickness of 100nm has been deposed on a silicon substrate in the absence of nitrogen, and then a 3nm Si thin film to cover carbon layer was deposed. Further, seven Si and C layers were alternatively deposed in the presence of nitrogen ions, each having a thickness of 40nm. In order to form silicon carbide at the interface between silicon and carbon layers, all carbon, silicon and nitrogen ions energy has increased up to 150eV . The characterization of microstructure and electrical properties of as-prepared N-Si-C multilayer structures were done using Transmission Electron Microscopy (TEM, STEM) techniques, Thermal Desorption Spectroscopy (TDS) and electrical measurements. Oxidation protection of carbon is based on the reaction between oxygen and silicon carbide, resulting in SiO2, SiO and CO2, and also by reaction involving N, O and Si, resulting in silicon oxynitride (SiNxOy) with a continuously variable composition, and on the other hand, since nitrogen acts as a trapping barrier for oxygen. To perform electrical measurements, 80% silver filled two-component epoxy-based glue ohmic contacts were attached on the N-Si-C samples. Electrical conductivity was measured in constant current mode. The experimental data show the increase of conductivity with the increase of the nitrogen content. To explain the temperature behavior of electrical conductivity we assumed a thermally activated electric transport mechanism.

Spectral Indices to Monitor Nitrogen-Driven Carbon Uptake in Field Corn

Science.gov (United States)

Corp, Lawrence A.; Middleton, Elizabeth M.; Campbell, Peya E.; Huemmrich, K. Fred; Daughtry, Craig S. T.; Russ, Andrew; Cheng, Yen-Ben

2010-01-01

Climate change is heavily impacted by changing vegetation cover and productivity with large scale monitoring of vegetation only possible with remote sensing techniques. The goal of this effort was to evaluate existing reflectance (R) spectroscopic methods for determining vegetation parameters related to photosynthetic function and carbon (C) dynamics in plants. Since nitrogen (N) is a key constituent of photosynthetic pigments and C fixing enzymes, biological C sequestration is regulated in part by N availability. Spectral R information was obtained from field corn grown at four N application rates (0, 70, 140, 280 kg N/ha). A hierarchy of spectral observations were obtained: leaf and canopy with a spectral radiometer; aircraft with the AISA sensor; and satellite with EO-1 Hyperion. A number of spectral R indices were calculated from these hyperspectral observations and compared to geo-located biophysical measures of plant growth and physiological condition. Top performing indices included the R derivative index D730/D705 and the normalized difference of R750 vs. R705 (ND705), both of which differentiated three of the four N fertilization rates at multiple observation levels and yielded high correlations to these carbon parameters: light use efficiency (LUE); C:N ratio; and crop grain yield. These results advocate the use of hyperspectral sensors for remotely monitoring carbon cycle dynamics in managed terrestrial ecosystems.

Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance

International Nuclear Information System (INIS)

Zhai, Yunbo; Xu, Bibo; Zhu, Yun; Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming

2016-01-01

Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH 3 . We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH 3 at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH 3 , leads to a low surface area down to 458 m 2 /g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~ 4 at.% carbon atoms and part of oxygen function groups reacted with NH 3 . When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g). - Highlights: • The nitrogen content up to 10.43 at % during CAC pyrolysis under NH3 at 800 °C. • The oxygen groups and carbon atoms played an important role in the nitrogen doping. • NAC-600 shows a much higher specific capacitance than CAC.

Influence of stocking, site quality, stand age, low-severity canopy disturbance, and forest composition on sub-boreal aspen mixedwood carbon stocks

Science.gov (United States)

Reinikainen, Michael; D’Amato, Anthony W.; Bradford, John B.; Fraver, Shawn

2014-01-01

Low-severity canopy disturbance presumably influences forest carbon dynamics during the course of stand development, yet the topic has received relatively little attention. This is surprising because of the frequent occurrence of such events and the potential for both the severity and frequency of disturbances to increase as a result of climate change. We investigated the impacts of low-severity canopy disturbance and average insect defoliation on forest carbon stocks and rates of carbon sequestration in mature aspen mixedwood forests of varying stand age (ranging from 61 to 85 years), overstory composition, stocking level, and site quality. Stocking level and site quality positively affected the average annual aboveground tree carbon increment (CAAI), while stocking level, site quality, and stand age positively affected tree carbon stocks (CTREE) and total ecosystem carbon stocks (CTOTAL). Cumulative canopy disturbance (DIST) was reconstructed using dendroecological methods over a 29-year period. DIST was negatively and significantly related to soil carbon (CSOIL), and it was negatively, albeit marginally, related to CTOTAL. Minima in the annual aboveground carbon increment of trees (CAI) occurred at sites during defoliation of aspen (Populus tremuloides Michx.) by forest tent caterpillar (Malacosoma disstria Hubner), and minima were more extreme at sites dominated by trembling aspen than sites mixed with conifers. At sites defoliated by forest tent caterpillar in the early 2000s, increased sequestration by the softwood component (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss) compensated for overall decreases in CAI by 17% on average. These results underscore the importance of accounting for low-severity canopy disturbance events when developing regional forest carbon models and argue for the restoration and maintenance of historically important conifer species within aspen mixedwoods to enhance stand-level resilience to disturbance agents and maintain

Direct estimation of aboveground forest productivity through hyperspectral remote sensing of canopy nitrogen

Science.gov (United States)

Marie-Louise Smith; Scott V. Ollinger; Mary E. Martin; John D. Aber; Richard A. Hallett; Christine L. Goodale

2002-01-01

The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf-level photosynthesis, it has rarely...

Nitrogen: Unraveling the Secret to Stable Carbon-Supported Pt-Alloy Electrocatalysts

Science.gov (United States)

2013-10-01

release; distribution is unlimited. Nitrogen: unraveling the secret to stable carbon-supported Pt- alloy electrocatalysts The views, opinions and/or...Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy electrocatalysts Report Title Nitrogen functionalities significantly improve...design and optimization of next generation high performance catalyst materials. Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy

Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance

Energy Technology Data Exchange (ETDEWEB)

Zhai, Yunbo, E-mail: ybzhai@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Xu, Bibo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Zhu, Yun [Office of Scientific R& D, Hunan University, Changsha 410082 (China); Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

2016-04-01

Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH{sub 3}. We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH{sub 3} at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH{sub 3}, leads to a low surface area down to 458 m{sup 2}/g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~ 4 at.% carbon atoms and part of oxygen function groups reacted with NH{sub 3}. When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g). - Highlights: • The nitrogen content up to 10.43 at % during CAC pyrolysis under NH3 at 800 °C. • The oxygen groups and carbon atoms played an important role in the nitrogen doping. • NAC-600 shows a much higher specific capacitance than CAC.

Structure and photoluminescence of boron and nitrogen co-doped carbon nanorods

Energy Technology Data Exchange (ETDEWEB)

Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Gao, B. [College of Computer Science, Chongqing University, Chongqing 400044 (China); Chongqing Municipal Education Examinations Authority, Chongqing 401147 (China); Zhong, X.X., E-mail: xxzhong@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Shao, R.W.; Zheng, K. [Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

2016-07-15

Graphical abstract: Boron- and nitrogen- doped carbon nanorods. - Highlights: • The co-doping of nitrogen and boron in carbon nanorods. • The doping mechanism of nitrogen and boron in carbon nanorods by plasma. • Photoluminescence properties of nitrogen- and boron-doped carbon nanorods. - Abstract: Boron and nitrogen doped carbon nanorods (BNCNRs) were synthesized by plasma-enhanced hot filament chemical vapor deposition, where methane, nitrogen and hydrogen were used as the reaction gases and boron carbide was the boron source. The results of scanning electron microscopy, micro-Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicate that boron and nitrogen can be used as co-dopants in amorphous carbon nanorods. Combined with the characterization results, the doping mechanism was studied. The mechanism is used to explain the formation of different carbon materials by different methods. The photoluminescence (PL) properties of BNCNRs were studied. The PL results show that the BNCNRs generate strong green PL bands and weak blue PL bands, and the PL intensity lowered due to the doping of boron. The outcomes advance our knowledge on the synthesis and optical properties of carbon-based nanomaterials and contribute to the development of optoelectronic nanodevices based on nano-carbon mateirals.

Nitrogen/Sulfur-Codoped Carbon Materials from Chitosan for Supercapacitors

Science.gov (United States)

Li, Mei; Han, Xianlong; Chang, Xiaoqing; Yin, Wenchao; Ma, Jingyun

2016-08-01

d-Methionine and chitosan have been used for fabrication of nitrogen/sulfur-codoped carbon materials by a hydrothermal process followed by carbonization at 750°C for 3 h. The as-prepared carbon materials showed enhanced electrochemical performance, combining electrical double-layer capacitance with pseudocapacitance owing to the doping with sulfur and nitrogen. The specific capacitance of the obtained carbon material reached 135 F g-1 at current density of 1 A g-1, which is much higher than undoped chitosan (67 F g-1). The capacitance retention of the carbon material was almost 97.2% after 5000 cycles at current density of 1 A g-1. With such improved electrochemical performance, the nitrogen/sulfur-codoped carbon material may have promising potential for use in energy-storage electrodes of supercapacitors.

A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

International Nuclear Information System (INIS)

Ombaka, L.M.; Ndungu, P.G.; Omondi, B.; McGettrick, J.D.; Davies, M.L.; Nyamori, V.O.

2016-01-01

Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF_3 and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF_3 catalyst indicates that steric factors influence the X-ray structure of 1,1′-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF_3 catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and are less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF_3 and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF_3 catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials. - Graphical abstract: Graphical abstract showing the synthesis of N-CNTs using halogenated-ferrocenyl derivatives as catalyst with pyridine or acetonitrile as nitrogen and carbon sources via the chemical vapour deposition technique. - Highlights: • N-CNTs were synthesized from halogenated ferrocenyl catalysts. • Halogenated catalysts promote nitrogen-doping and pyridinic nitrogen in N-CNTs. • Halogenated catalysts facilitate iron filling of N-CNTs.

Carbon-nitrogen interactions and biomass partitioning of Carex rostrata grown at three levels of nitrogen supply

Energy Technology Data Exchange (ETDEWEB)

Saarinen, T [Helsinki Univ. (Finland). Dept. of Ecology and Systematics

1997-12-31

Biomass and production of vascular plants constitutes a major source of carbon input in peatlands. As rates of decomposition vary considerably with depth, the vertical distribution of biomass may substantially affect accumulation of carbon in peatlands. Therefore, allocation patterns between shoot and roots are particularly important when considering carbon balance of peatland ecosystems. The stimulatory effect of increasing atmospheric concentration of CO{sub 2} or photosynthesis may increase availability of carbon to most C3 plants. Availability of nitrogen may also alter both due to increased atmospheric deposition and changer in mineralisation rates associated with climate change. Most root-shoot partitioning models predict that allocation of biomass is dependent of the availability and uptake of carbon and nitrogen. A decrease in supply of carbon would favour allocation to shoots and a decrease in supply of nitrogen would increase allocation to roots. At a cellular level, non structural carbohydrates and free amino acids are thought to represent the biochemically available fraction of carbon and nitrogen, respectively. The aim of this work is study the long-term growth responses of Carex rostrata to changes in the availability of nitrogen. Special attention is paid to soluble sugars ant free amino acids, which may control partitioning of biomass. (10 refs.)

Carbon-nitrogen interactions and biomass partitioning of Carex rostrata grown at three levels of nitrogen supply

Energy Technology Data Exchange (ETDEWEB)

Saarinen, T. [Helsinki Univ. (Finland). Dept. of Ecology and Systematics

1996-12-31

Biomass and production of vascular plants constitutes a major source of carbon input in peatlands. As rates of decomposition vary considerably with depth, the vertical distribution of biomass may substantially affect accumulation of carbon in peatlands. Therefore, allocation patterns between shoot and roots are particularly important when considering carbon balance of peatland ecosystems. The stimulatory effect of increasing atmospheric concentration of CO{sub 2} or photosynthesis may increase availability of carbon to most C3 plants. Availability of nitrogen may also alter both due to increased atmospheric deposition and changer in mineralisation rates associated with climate change. Most root-shoot partitioning models predict that allocation of biomass is dependent of the availability and uptake of carbon and nitrogen. A decrease in supply of carbon would favour allocation to shoots and a decrease in supply of nitrogen would increase allocation to roots. At a cellular level, non structural carbohydrates and free amino acids are thought to represent the biochemically available fraction of carbon and nitrogen, respectively. The aim of this work is study the long-term growth responses of Carex rostrata to changes in the availability of nitrogen. Special attention is paid to soluble sugars ant free amino acids, which may control partitioning of biomass. (10 refs.)

Sub-ambient carbon dioxide adsorption properties of nitrogen doped graphene

Energy Technology Data Exchange (ETDEWEB)

Tamilarasan, P.; Ramaprabhu, Sundara, E-mail: ramp@iitm.ac.in [Alternative Energy and Nanotechnology Laboratory (AENL), Nano Functional Materials Technology Centre (NFMTC), Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

2015-04-14

Carbon dioxide adsorption on carbon surface can be enhanced by doping the surface with heterogeneous atoms, which can increase local surface affinity. This study presents the carbon dioxide adsorption properties of nitrogen doped graphene at low pressures (<100 kPa). Graphene was exposed to nitrogen plasma, which dopes nitrogen atoms into carbon hexagonal lattice, mainly in pyridinic and pyrrolic forms. It is found that nitrogen doping significantly improves the CO{sub 2} adsorption capacity at all temperatures, due to the enrichment of local Lewis basic sites. In general, isotherm and thermodynamic parameters suggest that doped nitrogen sites have nearly same adsorption energy of surface defects and residual functional groups. The isosteric heat of adsorption remains in physisorption range, which falls with surface coverage, suggesting the distribution of magnitude of adsorption energy. The absolute values of isosteric heat and entropy of adsorption are slightly increased upon nitrogen doping.

Carbon-nitrogen-water interactions: is model parsimony fruitful?

Science.gov (United States)

Puertes, Cristina; González-Sanchis, María; Lidón, Antonio; Bautista, Inmaculada; Lull, Cristina; Francés, Félix

2017-04-01

It is well known that carbon and nitrogen cycles are highly intertwined and both should be explained through the water balance. In fact, in water-controlled ecosystems nutrient deficit is related to this water scarcity. For this reason, the present study compares the capability of three models in reproducing the interaction between the carbon and nitrogen cycles and the water cycle. The models are BIOME-BGCMuSo, LEACHM and a simple carbon-nitrogen model coupled to the hydrological model TETIS. Biome-BGCMuSo and LEACHM are two widely used models that reproduce the carbon and nitrogen cycles adequately. However, their main limitation is that these models are quite complex and can be too detailed for watershed studies. On the contrary, the TETIS nutrient sub-model is a conceptual model with a vertical tank distribution over the active soil depth, dividing it in two layers. Only the input of the added litter and the losses due to soil respiration, denitrification, leaching and plant uptake are considered as external fluxes. Other fluxes have been neglected. The three models have been implemented in an experimental plot of a semi-arid catchment (La Hunde, East of Spain), mostly covered by holm oak (Quercus ilex). Plant transpiration, soil moisture and runoff have been monitored daily during nearly two years (26/10/2012 to 30/09/2014). For the same period, soil samples were collected every two months and taken to the lab in order to obtain the concentrations of dissolved organic carbon, microbial biomass carbon, ammonium and nitrate. In addition, between field trips soil samples were placed in PVC tubes with resin traps and were left incubating (in situ buried cores). Thus, mineralization and nitrification accumulated fluxes for two months, were obtained. The ammonium and nitrate leaching accumulated for two months were measured using ion-exchange resin cores. Soil respiration was also measured every field trip. Finally, water samples deriving from runoff, were collected

Soil Carbon and Nitrogen Cycle Modeling

Science.gov (United States)

Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

2012-12-01

Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

The solubility of carbon in low-nitrogen liquid lithium

International Nuclear Information System (INIS)

Yonco, R.M.; Homa, M.I.

1986-01-01

The solubility of carbon in liquid lithium containing 0 C and compared with the solubility in lithium containing proportional 2600 wppm nitrogen in that same temperature range. A direct sampling method was employed in which filtered samples of the saturated solution were taken at randomly selected temperatures. The entire sample was analyzed for carbon by the acetylene evolution method. The analytical method was examined critically and it was found that (1) all of the carbon in solution, including carbon introduced as lithium cyanamide is detected and (2) ethylene and ethane must also be measured and included with the acetylene to get complete recovery of the carbon content of the sample. The solubility of carbon in low-nitrogen lithium can be expressed by the equations ln S=6.731-8617T -1 and log Ssup(*)=7.459-3740T -1 , where S is the mole percent Li 2 C 2 and Ssup(*) is in weight parts per million carbon. The presence of proportional 2600 wppm nitrogen does not affect the solubility of carbon in lithium at temperatures above proportional 350 0 C, but at lower temperatures it increased the solubility by as much as an order of magnitude compared to the solubility in low-nitrogen lithium. (orig.)

Variation in foliar nitrogen and albedo in response to nitrogen fertilization and elevated CO2

Science.gov (United States)

Haley F. Wicklein; Scott V. Ollinger; Mary E. Martin; David Y. Hollinger; Lucie C. Lepine; Michelle C. Day; Megan K. Bartlett; Andrew D. Richardson; Richard J. Norby

2012-01-01

Foliar nitrogen has been shown to be positively correlated with midsummer canopy albedo and canopy near infrared (NIR) reflectance over a broad range of plant functional types (e.g., forests, grasslands, and agricultural lands). To date, the mechanism(s) driving the nitrogen-albedo relationship have not been established, and it is unknown whether factors affecting...

Biomass derived porous nitrogen doped carbon for electrochemical devices

Directory of Open Access Journals (Sweden)

Litao Yan

2017-04-01

Full Text Available Biomass derived porous nanostructured nitrogen doped carbon (PNC has been extensively investigated as the electrode material for electrochemical catalytic reactions and rechargeable batteries. Biomass with and without containing nitrogen could be designed and optimized to prepare PNC via hydrothermal carbonization, pyrolysis, and other methods. The presence of nitrogen in carbon can provide more active sites for ion absorption, improve the electronic conductivity, increase the bonding between carbon and sulfur, and enhance the electrochemical catalytic reaction. The synthetic methods of natural biomass derived PNC, heteroatomic co- or tri-doping into biomass derived carbon and the application of biomass derived PNC in rechargeable Li/Na batteries, high energy density Li–S batteries, supercapacitors, metal-air batteries and electrochemical catalytic reaction (oxygen reduction and evolution reactions, hydrogen evolution reaction are summarized and discussed in this review. Biomass derived PNCs deliver high performance electrochemical storage properties for rechargeable batteries/supercapacitors and superior electrochemical catalytic performance toward hydrogen evolution, oxygen reduction and evolution, as promising electrodes for electrochemical devices including battery technologies, fuel cell and electrolyzer. Keywords: Biomass, Nitrogen doped carbon, Batteries, Fuel cell, Electrolyzer

Effect of various carbon and nitrogen sources on cellulose synthesis ...

African Journals Online (AJOL)

The effect of various carbon and nitrogen sources on cellulose production by Acetobacter lovaniensis HBB5 was examined. In this study, glucose, fructose, sucrose and ethanol as carbon source and yeast extract, casein hydrolysate and ammonium sulphate as nitrogen source were used. Among the carbon sources, ...

Carbon and nitrogen stoichiometry across stream ecosystems

Science.gov (United States)

Wymore, A.; Kaushal, S.; McDowell, W. H.; Kortelainen, P.; Bernhardt, E. S.; Johnes, P.; Dodds, W. K.; Johnson, S.; Brookshire, J.; Spencer, R.; Rodriguez-Cardona, B.; Helton, A. M.; Barnes, R.; Argerich, A.; Haq, S.; Sullivan, P. L.; López-Lloreda, C.; Coble, A. A.; Daley, M.

2017-12-01

Anthropogenic activities are altering carbon and nitrogen concentrations in surface waters globally. The stoichiometry of carbon and nitrogen regulates important watershed biogeochemical cycles; however, controls on carbon and nitrogen ratios in aquatic environments are poorly understood. Here we use a multi-biome and global dataset (tropics to Arctic) of stream water chemistry to assess relationships between dissolved organic carbon (DOC) and nitrate, ammonium and dissolved organic nitrogen (DON), providing a new conceptual framework to consider interactions between DOC and the multiple forms of dissolved nitrogen. We found that across streams the total dissolved nitrogen (TDN) pool is comprised of very little ammonium and as DOC concentrations increase the TDN pool shifts from nitrate to DON dominated. This suggests that in high DOC systems, DON serves as the primary source of nitrogen. At the global scale, DOC and DON are positively correlated (r2 = 0.67) and the average C: N ratio of dissolved organic matter (molar ratio of DOC: DON) across our data set is approximately 31. At the biome and smaller regional scale the relationship between DOC and DON is highly variable (r2 = 0.07 - 0.56) with the strongest relationships found in streams draining the mixed temperate forests of the northeastern United States. DOC: DON relationships also display spatial and temporal variability including latitudinal and seasonal trends, and interactions with land-use. DOC: DON ratios correlated positively with gradients of energy versus nutrient limitation pointing to the ecological role (energy source versus nutrient source) that DON plays with stream ecosystems. Contrary to previous findings we found consistently weak relationships between DON and nitrate which may reflect DON's duality as an energy or nutrient source. Collectively these analyses demonstrate how gradients of DOC drive compositional changes in the TDN pool and reveal a high degree of variability in the C: N ratio

Electrocatalysis of oxygen reduction on nitrogen-containing multi-walled carbon nanotube modified glassy carbon electrodes

International Nuclear Information System (INIS)

Vikkisk, Merilin; Kruusenberg, Ivar; Joost, Urmas; Shulga, Eugene; Tammeveski, Kaido

2013-01-01

Highlights: ► Pyrolysis in the presence of urea was used for nitrogen doping of carbon nanotubes. ► N-doped carbon nanotubes were used as catalysts for the oxygen reduction reaction. ► N-doped carbon material showed a high catalytic activity for ORR in alkaline media. ► N-containing CNT material is an attractive cathode catalyst for alkaline membrane fuel cells. - Abstract: The electrochemical reduction of oxygen was studied on nitrogen-doped multi-walled carbon nanotube (NCNT) modified glassy carbon (GC) electrodes employing the rotating disk electrode (RDE) method. Nitrogen doping was achieved by simple pyrolysis of the carbon nanotube material in the presence of urea. The surface morphology and composition of the NCNT samples were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed a rather uniform distribution of NCNTs on the GC electrode substrate. The XPS analysis showed a successful doping of carbon nanotubes with nitrogen species. The RDE results revealed that in alkaline solution the N-doped nanotube materials showed a remarkable electrocatalytic activity towards oxygen reduction. At low overpotentials the reduction of oxygen followed a two-electron pathway on undoped carbon nanotube modified GC electrodes, whereas on NCNT/GC electrodes a four-electron pathway of O 2 reduction predominated. The results obtained are significant for the development of nitrogen-doped carbon-based cathodes for alkaline membrane fuel cells.

Amazon forest carbon dynamics predicted by profiles of canopy leaf area and light environment

Science.gov (United States)

S. C. Stark; V. Leitold; J. L. Wu; M. O. Hunter; C. V. de Castilho; F. R. C. Costa; S. M. McMahon; G. G. Parker; M. Takako Shimabukuro; M. A. Lefsky; M. Keller; L. F. Alves; J. Schietti; Y. E. Shimabukuro; D. O. Brandao; T. K. Woodcock; N. Higuchi; P. B de Camargo; R. C. de Oliveira; S. R. Saleska

2012-01-01

Tropical forest structural variation across heterogeneous landscapes may control above-ground carbon dynamics. We tested the hypothesis that canopy structure (leaf area and light availability) – remotely estimated from LiDAR – control variation in above-ground coarse wood production (biomass growth). Using a statistical model, these factors predicted biomass growth...

Sequestration of Carbon in Mycorrhizal Fungi Under Nitrogen Fertilization

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Treseder, K. K.; Turner, K. M.

2005-12-01

Mycorrhizal fungi are root symbionts that facilitate plant uptake of soil nutrients in exchange for plant carbohydrates. They grow in almost every terrestrial ecosystem on earth, form relationships with about 80% of plant species, and receive 10 to 20% of the carbon fixed by their host plants. As such, they could potentially sequester a significant amount of carbon in ecosystems. We hypothesized that nitrogen fertilization would decrease carbon storage in mycorrhizal fungi, because plants should reduce investment of carbon in mycorrhizal fungi when nitrogen availability is high. We measured the abundance of two major groups of mycorrhizal fungi, arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi, in control and nitrogen-fertilized plots within three boreal ecosystems of inland Alaska. The ecosystems represented different recovery stages following severe fire, and comprised a young site dominated by AM fungi, an old site dominated by ECM fungi, and an intermediate site co-dominated by both groups. Pools of mycorrhizal carbon included root-associated AM and ECM structures, soil-associated AM hyphae, and soil-associated glomalin. Glomalin is a glycoprotein produced only by AM fungi. It is present in the cell walls of AM hyphae, and then is deposited in the soil as the hyphae senesce. Nitrogen significantly altered total mycorrhizal carbon pools, but its effect varied by site (site * N interaction, P = 0.05). Under nitrogen fertilization, mycorrhizal carbon was reduced from 99 to 50 g C m2 in the youngest site, was increased from 124 to 203 g C m2 in the intermediate-aged site, and remained at 35 g C m2 in the oldest site. The changes in total mycorrhizal carbon stocks were driven mostly by changes in glomalin (site * N interaction, P = 0.05), and glomalin stocks were strongly correlated with AM hyphal abundance (P stocks within root-associated AM structures increased significantly with nitrogen fertilization across all sites (P = 0.001), as did root

Nitrogen doped silicon-carbon multilayer protective coatings on carbon obtained by thermionic vacuum arc (TVA) method

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Ciupinǎ, Victor; Vasile, Eugeniu; Porosnicu, Corneliu; Vladoiu, Rodica; Mandes, Aurelia; Dinca, Virginia; Nicolescu, Virginia; Manu, Radu; Dinca, Paul; Zaharia, Agripina

2018-02-01

To obtain protective nitrogen doped Si-C multilayer coatings on carbon, used to improve the oxidation resistance of carbon, was used TVA method. The initial carbon layer has been deposed on a silicon substrate in the absence of nitrogen, and then a 3nm Si thin film to cover carbon layer was deposed. Further, seven Si and C layers were alternatively deposed in the presence of nitrogen ions. In order to form silicon carbide at the interface between silicon and carbon layers, all carbon, silicon and nitrogen ions energy has increased up to 150eV. The characterization of microstructure and electrical properties of as-prepared N-Si-C multilayer structures were done using Transmission Electron Microscopy (TEM, STEM) techniques, Thermal Desorption Spectroscopy (TDS) and electrical measurements. The retention of oxygen in the protective layer of N-Si-C is due to the following phenomena: (a) The reaction between oxygen and silicon carbide resulting in silicon oxide and carbon dioxide; (b) The reaction involving oxygen, nitrogen and silicon resulting silicon oxinitride with a variable composition; (c) Nitrogen acts as a trapping barrier for oxygen. To perform electrical measurements, ohmic contacts were attached on the N-Si-C samples. Electrical conductivity was measured in constant current mode. To explain the temperature behavior of electrical conductivity we assumed a thermally activated electric transport mechanism.

Bacterial nitrogen fixation in sand bioreactors treating winery wastewater with a high carbon to nitrogen ratio.

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Welz, Pamela J; Ramond, Jean-Baptiste; Braun, Lorenz; Vikram, Surendra; Le Roes-Hill, Marilize

2018-02-01

Heterotrophic bacteria proliferate in organic-rich environments and systems containing sufficient essential nutrients. Nitrogen, phosphorus and potassium are the nutrients required in the highest concentrations. The ratio of carbon to nitrogen is an important consideration for wastewater bioremediation because insufficient nitrogen may result in decreased treatment efficiency. It has been shown that during the treatment of effluent from the pulp and paper industry, bacterial nitrogen fixation can supplement the nitrogen requirements of suspended growth systems. This study was conducted using physicochemical analyses and culture-dependent and -independent techniques to ascertain whether nitrogen-fixing bacteria were selected in biological sand filters used to treat synthetic winery wastewater with a high carbon to nitrogen ratio (193:1). The systems performed well, with the influent COD of 1351 mg/L being reduced by 84-89%. It was shown that the nitrogen fixing bacterial population was influenced by the presence of synthetic winery effluent in the surface layers of the biological sand filters, but not in the deeper layers. It was hypothesised that this was due to the greater availability of atmospheric nitrogen at the surface. The numbers of culture-able nitrogen-fixing bacteria, including presumptive Azotobacter spp. exhibited 1-2 log increases at the surface. The results of this study confirm that nitrogen fixation is an important mechanism to be considered during treatment of high carbon to nitrogen wastewater. If biological treatment systems can be operated to stimulate this phenomenon, it may obviate the need for nitrogen addition. Copyright © 2017 Elsevier Ltd. All rights reserved.

In situ one-step synthesis of hierarchical nitrogen-doped porous carbon for high-performance supercapacitors.

Science.gov (United States)

Jeon, Ju-Won; Sharma, Ronish; Meduri, Praveen; Arey, Bruce W; Schaef, Herbert T; Lutkenhaus, Jodie L; Lemmon, John P; Thallapally, Praveen K; Nandasiri, Manjula I; McGrail, Benard Peter; Nune, Satish K

2014-05-28

A hierarchically structured nitrogen-doped porous carbon is prepared from a nitrogen-containing isoreticular metal-organic framework (IRMOF-3) using a self-sacrificial templating method. IRMOF-3 itself provides the carbon and nitrogen content as well as the porous structure. For high carbonization temperatures (950 °C), the carbonized MOF required no further purification steps, thus eliminating the need for solvents or acid. Nitrogen content and surface area are easily controlled by the carbonization temperature. The nitrogen content decreases from 7 to 3.3 at % as carbonization temperature increases from 600 to 950 °C. There is a distinct trade-off between nitrogen content, porosity, and defects in the carbon structure. Carbonized IRMOFs are evaluated as supercapacitor electrodes. For a carbonization temperature of 950 °C, the nitrogen-doped porous carbon has an exceptionally high capacitance of 239 F g(-1). In comparison, an analogous nitrogen-free carbon bears a low capacitance of 24 F g(-1), demonstrating the importance of nitrogen dopants in the charge storage process. The route is scalable in that multi-gram quantities of nitrogen-doped porous carbons are easily produced.

Water stress effects on spatially referenced cotton crop canopy properties

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rop canopy temperature is known to be affected by water stress. Canopy reflectance can also be impacted as leaf orientation and color respond to the stress. As sensor systems are investigated for real-time management of irrigation and nitrogen, it is essential to understand how the data from the sen...

A Two-Big-Leaf Model for Canopy Temperature, Photosynthesis, and Stomatal Conductance.

Science.gov (United States)

Dai, Yongjiu; Dickinson, Robert E.; Wang, Ying-Ping

2004-06-01

The energy exchange, evapotranspiration, and carbon exchange by plant canopies depend on leaf stomatal control. The treatment of this control has been required by land components of climate and carbon models. Physiological models can be used to simulate the responses of stomatal conductance to changes in atmospheric and soil environments. Big-leaf models that treat a canopy as a single leaf tend to overestimate fluxes of CO2 and water vapor. Models that differentiate between sunlit and shaded leaves largely overcome these problems.A one-layered, two-big-leaf submodel for photosynthesis, stomatal conductance, leaf temperature, and energy fluxes is presented in this paper. It includes 1) an improved two stream approximation model of radiation transfer of the canopy, with attention to singularities in its solution and with separate integrations of radiation absorption by sunlit and shaded fractions of canopy; 2) a photosynthesis stomatal conductance model for sunlit and shaded leaves separately, and for the simultaneous transfers of CO2 and water vapor into and out of the leaf—leaf physiological properties (i.e., leaf nitrogen concentration, maximum potential electron transport rate, and hence photosynthetic capacity) vary throughout the plant canopy in response to the radiation weight time-mean profile of photosynthetically active radiation (PAR), and the soil water limitation is applied to both maximum rates of leaf carbon uptake by Rubisco and electron transport, and the model scales up from leaf to canopy separately for all sunlit and shaded leaves; 3) a well-built quasi-Newton Raphson method for simultaneous solution of temperatures of the sunlit and shaded leaves.The model was incorporated into the Common Land Model (CLM) and is denoted CLM 2L. It was driven with observational atmospheric forcing from two forest sites [Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) and Boreal Ecosystem Atmosphere Study (BOREAS)] for 2 yr of simulation. The

Modeling percent tree canopy cover: a pilot study

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John W. Coulston; Gretchen G. Moisen; Barry T. Wilson; Mark V. Finco; Warren B. Cohen; C. Kenneth Brewer

2012-01-01

Tree canopy cover is a fundamental component of the landscape, and the amount of cover influences fire behavior, air pollution mitigation, and carbon storage. As such, efforts to empirically model percent tree canopy cover across the United States are a critical area of research. The 2001 national-scale canopy cover modeling and mapping effort was completed in 2006,...

Forest canopy temperatures: dynamics, controls, and relationships with ecosystem fluxes

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Still, C. J.; Griffith, D.; Kim, Y.; Law, B. E.; Hanson, C. V.; Kwon, H.; Schulze, M.; Detto, M.; Pau, S.

2017-12-01

Temperature strongly affects enzymatic reactions, ecosystem biogeochemistry, and species distributions. Although most focus is on air temperature, the radiative or skin temperature of plants is more relevant. Canopy skin temperature dynamics reflect biophysical, physiological, and anatomical characteristics and interactions with the environment, and can be used to examine forest responses to stresses like droughts and heat waves. Thermal infrared (TIR) imaging allows for extensive temporal and spatial sampling of canopy temperatures, particularly compared to spot measurements using thermocouples. We present results of TIR imaging of forest canopies at eddy covariance flux tower sites in the US Pacific Northwest and in Panama. These forests range from an old-growth temperate rainforest to a second growth semi-arid pine forest to a semi-deciduous tropical forest. Canopy temperature regimes at these sites are highly variable. Canopy temperatures at all forest sites displayed frequent departures from air temperature, particularly during clear sky conditions, with elevated canopy temperatures during the day and depressed canopy temperatures at night compared to air temperature. Comparison of canopy temperatures to fluxes of carbon dioxide, water vapor, and energy reveals stronger relationships than those found with air temperature. Daytime growing season net ecosystem exchange at the pine forest site is better explained by canopy temperature (r2 = 0.61) than air temperature (r2 = 0.52). At the semi-deciduous tropical forest, canopy photosynthesis is highly correlated with canopy temperature (r2 = 0.51), with a distinct optimum temperature for photosynthesis ( 31 °C) that agrees with leaf-level measurements. During the peak of one heat wave at an old-growth temperate rainforest, hourly averaged air temperature exceeded 35 °C, 10 °C above average. Peak hourly canopy temperature approached 40 °C, and leaf-to-air vapor pressure deficit exceeded 6 kPa. These extreme

Carbonization-dependent nitrogen-doped hollow porous carbon nanospheres synthesis and electrochemical study for supercapacitors

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Zhou, Lingyun; Xie, Guohong; Chen, Xiling

2018-05-01

In this paper, a nitrogen-doped hollow microporous carbon nanospheres was synthesized via the combination of hyper-crosslinking mediated self-assembly and further pyrolysis using polylactide-b-polystyrene (PLA-b-PS) copolymers and aniline monomers as precursor. The pore structure and the correlative electrochemical performance of nitrogen-doped hollow microporous carbon nanospheres were affected by the molar mass ratio of aniline and PS in block copolymers and the carbonization conditions. The electrochemical measurements results showed that the obtained PLA150-PS250-N4-900-10H sample with nitrogen content of 3.57% and the BET surface area of 945 m2 g-1 displays the best capacitance performance. At a current density of 1.0 Ag-1, the resultant specific capacitance is 250 Fg-1. In addition, it also exhibits high capacitance retention of 98% after charging-discharging 1500 times at 25 Ag-1. The results demonstrate the nitrogen-doped hollow microporous carbon nanospheres can be used as promising supercapacitor electrode materials for high performance energy storage devices.

Biophysical Controls over Carbon and Nitrogen Stocks in Desert Playa Wetlands

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McKenna, O. P.; Sala, O. E.

2014-12-01

Playas are ephemeral desert wetlands situated at the bottom of closed catchments. Desert playas in the Southwestern US have not been intensively studied despite their potential importance for the functioning of desert ecosystems. We want to know which geomorphic and ecological variables control of the stock size of soil organic carbon, and soil total nitrogen in playas. We hypothesize that the magnitude of carbon and nitrogen stocks depends on: (a) catchment size, (b) catchment slope, (d) catchment vegetation cover, (e) bare-ground patch size, and (f) catchment soil texture. We chose thirty playas from across the Jornada Basin (Las Cruces, NM) ranging from 0.5-60ha in area and with varying catchment characteristics. We used the available 5m digital elevation map (DEM) to calculate the catchment size and catchment slope for these thirty playas. We measured percent cover, and patch size using the point-intercept method with three 10m transects in each catchment. We used the Bouyoucos-hydrometer soil particle analysis to determine catchment soil texture. Stocks of organic carbon and nitrogen were measured from soil samples at four depths (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm) using C/N combustion analysis. In terms of nitrogen and organic carbon storage, we found soil nitrogen values in the top 10cm ranging from 41.963-214.365 gN/m2, and soil organic carbon values in the top 10cm ranging from 594.339-2375.326 gC/m2. The results of a multiple regression analysis show a positive relationship between catchment slope and both organic carbon and nitrogen stock size (nitrogen: y= 56.801 +47.053, R2=0.621; organic carbon: y= 683.200 + 499.290x, R2= 0.536). These data support our hypothesis that catchment slope is one of factors controlling carbon and nitrogen stock in desert playas. We also applied our model to the 69 other playas of the Jornada Basin and estimated stock sizes (0-10cm) between 415.07-447.97 Mg for total soil nitrogen and 4627.99-5043.51 Mg for soil organic

Nitrogen-Rich Polyacrylonitrile-Based Graphitic Carbons for Hydrogen Peroxide Sensing

Directory of Open Access Journals (Sweden)

Brandon Pollack

2017-10-01

Full Text Available Catalytic substrate, which is devoid of expensive noble metals and enzymes for hydrogen peroxide (H2O2, reduction reactions can be obtained via nitrogen doping of graphite. Here, we report a facile fabrication method for obtaining such nitrogen doped graphitized carbon using polyacrylonitrile (PAN mats and its use in H2O2 sensing. A high degree of graphitization was obtained with a mechanical treatment of the PAN fibers embedded with carbon nanotubes (CNT prior to the pyrolysis step. The electrochemical testing showed a limit of detection (LOD 0.609 µM and sensitivity of 2.54 µA cm−2 mM−1. The promising sensing performance of the developed carbon electrodes can be attributed to the presence of high content of pyridinic and graphitic nitrogens in the pyrolytic carbons, as confirmed by X-ray photoelectron spectroscopy. The reported results suggest that, despite their simple fabrication, the hydrogen peroxide sensors developed from pyrolytic carbon nanofibers are comparable with their sophisticated nitrogen-doped graphene counterparts.

Canopy interactions of rainfall in an off-shore mangrove ecosystem dominated by Rhizophora mangle (Belize)

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Wanek, Wolfgang; Hofmann, Julia; Feller, Ilka C.

2007-10-01

SummaryBulk precipitation, throughfall and stemflow were collected to study anthropogenic effects on above-ground nutrient cycling in an off-shore mangrove forest ( Rhizophora mangle L.) on Twin Cays, Belize. Samples were collected in a nitrogen limited fringe and phosphorus limited dwarf zone, and from an adjacent nitrogen fertilized fringe and a phosphorus fertilized dwarf zone. Inorganic cations and anions, dissolved organic carbon (DOC) and nitrogen (DON) were analysed. Throughfall represented 84% of precipitation volume. Sea salt ions (Cl -, Na +, SO42- and Mg 2+) and DOC accounted for the highest proportion of solutes in rainwater, throughfall and stemflow in R. mangle stands. Non-marine sources dominated the flux of DON, DOC, NO3-, NH4+, and inorganic P (P i) in bulk precipitation and throughfall and partially contributed to Ca 2+ and K +. Deposition ratios (throughfall deposition:bulk deposition) showed that inorganic NH4+, and less so P i were retained in the canopy of R. mangle from throughfall while all other solutes increased. Canopy leaching contributed in increasing order to net throughfall of Ca 2+, Cl -, SO42-/K, Mg 2+ and Na + but dry deposition dominated the net throughfall flux during the investigated period. Fertilizer treatment and zone did only slightly affect solute concentrations of hot-water extracts of leaves, of throughfall and stemflow in stands of similar stature. While litterfall and primary production have previously been shown to increase substantially upon nutrient enrichment of mangroves we therefore conclude that fertilization, as a surrogate of anthropogenic eutrophication, may not increase nutrient leaching from mangrove canopies, and thus may only have a minor effect on soluble organic matter cycling and inputs into mangrove food webs.

Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

Directory of Open Access Journals (Sweden)

X. Yang

2010-10-01

Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

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Atul Jain; Xiaojuan Yang; Haroon Kheshgi; A. David McGuire; Wilfred Post; David. Kicklighter

2009-01-01

Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen...

Interrelationships among light, photosynthesis and nitrogen in the crown of mature Pinus contorta ssp. latifolia

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A. W. Schoettle; W. K. Smith

1999-01-01

Scaling leaf-level measurements to estimate carbon gain of entire leaf crowns or canopies requires an understanding of the distribution of photosynthetic capacity and corresponding light microenvironments within a crown. We have compared changes in the photosynthetic light response and nitrogen (N) content (per unit leaf area) of Pinus contorta Dougl. ssp. latifolia...

An Integrated Tool for Calculating and Reducing Institution Carbon and Nitrogen Footprints

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Galloway, James N.; Castner, Elizabeth A.; Andrews, Jennifer; Leary, Neil; Aber, John D.

2017-01-01

Abstract The development of nitrogen footprint tools has allowed a range of entities to calculate and reduce their contribution to nitrogen pollution, but these tools represent just one aspect of environmental pollution. For example, institutions have been calculating their carbon footprints to track and manage their greenhouse gas emissions for over a decade. This article introduces an integrated tool that institutions can use to calculate, track, and manage their nitrogen and carbon footprints together. It presents the methodology for the combined tool, describes several metrics for comparing institution nitrogen and carbon footprint results, and discusses management strategies that reduce both the nitrogen and carbon footprints. The data requirements for the two tools overlap substantially, although integrating the two tools does necessitate the calculation of the carbon footprint of food. Comparison results for five institutions suggest that the institution nitrogen and carbon footprints correlate strongly, especially in the utilities and food sectors. Scenario analyses indicate benefits to both footprints from a range of utilities and food footprint reduction strategies. Integrating these two footprints into a single tool will account for a broader range of environmental impacts, reduce data entry and analysis, and promote integrated management of institutional sustainability. PMID:29350217

Thermal and chemical durability of nitrogen-doped carbon nanotubes

International Nuclear Information System (INIS)

Liu Hao; Zhang Yong; Li Ruying; Sun Xueliang; Abou-Rachid, Hakima

2012-01-01

Nitrogen-doped carbon nanotubes (CN x tubes) with nitrogen content of 7.6 at.% are synthesized on carbon papers. Thermal and chemical stability of the nanotubes are investigated by thermogravimetric analysis, differential scanning calorimetry and X-ray photoelectron spectroscopy techniques. The results indicate that the nitrogen can be firmly kept in the nanotubes after annealing at 300 °C in air. Under an argon atmosphere, the nitrogen would not release until 670 °C, and half of the nitrogen incorporated is released after annealing at 700 °C for 30 min. Chemical stability investigation indicates that the nitrogen incorporated in the nanotubes is very stable under the thermal and acid environment comparable to working condition of proton exchange membrane (PEM) fuel cells. Profile of the nitrogen species inside the nanotubes reveals that graphite-like nitrogen releases slower than any other kind of nitrogen in the nanotubes during the chemical stability measurement. These CN x tubes synthesized by this simple chemical vapor deposition method are expected to be suitable for many applications, such as PEM fuel cells that work under both thermal and corrosive conditions and some other mild thermal environments.

The carbon-nitrogen balance of the nodule and its regulation under elevated carbon dioxide concentration.

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Libault, Marc

2014-01-01

Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN2). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency.

BOREAS TE-9 NSA Canopy Biochemistry

Science.gov (United States)

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Charest, Martin; Sy, Mikailou

2000-01-01

The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves. This data set contains canopy biochemistry data collected in 1994 in the NSA at the YJP, OJR, OBS, UBS, and OA sites, including biochemistry lignin, nitrogen, cellulose, starch, and fiber concentrations. These data were collected to study the spatial and temporal changes in the canopy biochemistry of boreal forest cover types and how a high-resolution radiative transfer model in the mid-infrared could be applied in an effort to obtain better estimates of canopy biochemical properties using remote sensing. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Evaluation of hydrologic equilibrium in a mountainous watershed: incorporating forest canopy spatial adjustment to soil biogeochemical processes

Science.gov (United States)

Mackay, D. Scott

Hydrologic equilibrium theory has been used to describe both short-term regulation of gas exchange and long-term adjustment of forest canopy density. However, by focusing on water and atmospheric conditions alone a hydrologic equilibrium may impose an oversimplification of the growth of forests adjusted to hydrology. In this study nitrogen is incorporated as a third regulation of catchment level forest dynamics and gas exchange. This was examined with an integrated distributed hydrology and forest growth model in a central Sierra Nevada watershed covered primarily by old-growth coniferous forest. Water and atmospheric conditions reasonably reproduced daily latent heat flux, and predicted the expected catenary trend of leaf area index (LAI). However, it was not until the model was provided a spatially detailed description of initial soil carbon and nitrogen pools that spatial patterns of LAI were generated. This latter problem was attributed to a lack of soil history or memory in the initialization of the simulations. Finally, by reducing stomatal sensitivity to vapor pressure deficit (VPD) the canopy density increased when water and nitrogen limitations were not present. The results support a three-control hydrologic equilibrium in the Sierra Nevada watershed. This has implications for modeling catchment level soil-vegetation-atmospheric interactions over interannual, decade, and century time-scales.

Nitrogen-Doped Carbon Dots as A New Substrate for Sensitive Glucose Determination

Directory of Open Access Journals (Sweden)

Hanxu Ji

2016-05-01

Full Text Available Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on nitrogen-doped carbon dots-modified carbon glassy electrodes by amino-carboxyl reactions. The nitrogen-induced charge delocalization at nitrogen-doped carbon dots can enhance the electrocatalytic activity toward the reduction of O2. The specific amino-carboxyl reaction provides strong and stable immobilization of GOx on electrodes. The developed biosensor responds efficiently to the presence of glucose in serum samples over the concentration range from 1 to 12 mM with a detection limit of 0.25 mM. This novel biosensor has good reproducibility and stability, and is highly selective for glucose determination under physiological conditions. These results indicate that N-doped quantum dots represent a novel candidate material for the construction of electrochemical biosensors.

A one-step carbonization route towards nitrogen-doped porous carbon hollow spheres with ultrahigh nitrogen content for CO 2 adsorption

KAUST Repository

Wang, Yu

2015-01-01

© The Royal Society of Chemistry 2015. Nitrogen doped porous carbon hollow spheres (N-PCHSs) with an ultrahigh nitrogen content of 15.9 wt% and a high surface area of 775 m² g^-1 were prepared using Melamine-formaldehyde nanospheres as hard templates and nitrogen sources. The N-PCHSs were completely characterized and were found to exhibit considerable CO2 adsorption performance (4.42 mmol g^-1).

Canopy Dynamics in Nanoscale Ionic Materials

KAUST Repository

Jespersen, Michael L.

2010-07-27

Nanoscale ionic materials (NIMS) are organic - inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. © 2010 American Chemical Society.

Canopy Dynamics in Nanoscale Ionic Materials

KAUST Repository

Jespersen, Michael L.; Mirau, Peter A.; Meerwall, Ernst von; Vaia, Richard A.; Rodriguez, Robert; Giannelis, Emmanuel P.

2010-01-01

Nanoscale ionic materials (NIMS) are organic - inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. © 2010 American Chemical Society.

Synthesis of polybenzoxazine based nitrogen-rich porous carbons for carbon dioxide capture

Science.gov (United States)

Wan, Liu; Wang, Jianlong; Feng, Chong; Sun, Yahui; Li, Kaixi

2015-04-01

Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the CO2 capture performance. At 1 bar, high CO2 uptake of 4.02 and 6.35 mmol g-1 at 25 and 0 °C was achieved for the sample NPC-2 with a molar ratio of F127 : urea = 0.010 : 1. This can be attributed to its well-developed micropore structure and abundant pyridinic nitrogen, pyrrolic nitrogen and pyridonic nitrogen functionalities. The sample NPC-2 also exhibits a remarkable selectivity for CO2/N2 separation and a fast adsorption/desorption rate and can be easily regenerated. This suggests that the polybenzoxazine-based NPCs are desirable for CO2 capture because of possessing a high micropore surface area, a large micropore volume, appropriate pore size distribution, and a large number of basic nitrogen functionalities.Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the

Hierarchically structured, nitrogen-doped carbon membranes

KAUST Repository

Wang, Hong; Wu, Tao

2017-01-01

The present invention is a structure, method of making and method of use for a novel macroscopic hierarchically structured, nitrogen-doped, nano-porous carbon membrane (HNDCMs) with asymmetric and hierarchical pore architecture that can be produced

Nitrogen-doped carbon based on peptides of hair as electrode materials for surpercapacitors

International Nuclear Information System (INIS)

Guo, Zihan; Zhou, Qingwen; Wu, Zhaojun; Zhang, Zhiguo; Zhang, Wen; Zhang, Yao; Li, Lijun; Cao, Zhenzhu; Wang, Hong; Gao, Yanfang

2013-01-01

Highlights: • Hair was directly carbonized by environmental and energy-saving methods. • Hair was utilized to prepare nitrogen-doped carbon materials for supercapacitor. • A new approache for preparing nitrogen-rich active carbon from biomass waste of hair-like precursor. • Hair-based carbon having a non-crystalline layered structure and excellent capacitive performance. -- Abstract: Hair, a high-nitrogen energetic material, is utilized as a precursor for nitrogen-doped porous carbon. The preparation procedures for obtaining carbon from hair are very simple, namely, reductant or deionized water activation process followed by hair carbonization under argon atmosphere at 800 °C for 2 h. The samples are characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption, and X-ray photoelectron microscopy. The carbon samples are tested as electrode materials in supercapacitors in a three-electrode system. The carbon (soaked in deionized water at 80 °C) presents relatively low specific surface areas (441.34 m 2 g −1 ) and shows higher capacitance (154.5 F g −1 ) compared with nitrogen-free commercial activated carbons (134.5 F g −1 ) at 5 A g −1 . The capacitance remains at 130.5 F g −1 even when the current load is increased to 15 A g −1 . The capacitance loss is only 5% in 6 M KOH after 10,000 charge and discharge cycles at 5 A g −1 . It is the unique microstructure after activation processing and electroactive nitrogen functionalities that enable the carbon obtained through a simple, ecological, and economical process to be utilized as a potential electrode material for electrical double-layer capacitors

A Compilation of Global Soil Microbial Biomass Carbon, Nitrogen, and Phosphorus Data

Data.gov (United States)

National Aeronautics and Space Administration — This data set provides the concentrations of soil microbial biomass carbon (C), nitrogen (N) and phosphorus (P), soil organic carbon, total nitrogen, and total...

Radiation and nitrogen use at the leaf and canopy level by wheat and oilseed rape during the critical period for grain number definition

International Nuclear Information System (INIS)

Dreccer, M.F.; Schapendonk, H.C.M.; Oijen, M. van; Pot, C.S.; Rabbinge, R.

2000-01-01

During the critical period for grain number definition, the amount of biomass produced per unit absorbed radiation is more sensitive to nitrogen (N) supply in oilseed rape than in wheat, and reaches a higher value at high N. This response was investigated by combining experimental and modelling work. Oilseed rape and wheat were grown at three levels of N supply, combined with two levels of plant density at high N supply. Canopy photosynthesis and daytime radiation use efficiency (RUE A ) were calculated with a model based on observed N-dependent leaf photosynthesis and observed canopy vertical distribution of light and leaf N. In oilseed rape, RUE A was higher than in wheat and, in contrast to wheat, the sensitivity to canopy leaf N content increased from the start to the end of the critical period. These results were partly explained by the higher leaf photosynthesis in oilseed rape vs wheat. In addition, oilseed rape leaves were increasingly shaded by the inflorescence. Thus, RUE A increased because more leaves were operating at non-saturating light levels. In both species, the vertical distribution of leaf N was close to that optimising canopy photosynthesis. The results are discussed in relation to possibilities for improvement of N productivity in these crops. (author)

Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

Science.gov (United States)

Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

2015-12-01

High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Nitrogen-to-carbon ratio in 70 dwarf halo stars

Energy Technology Data Exchange (ETDEWEB)

Carbon, D.F.; Kraft, R.P.; Barbuy, B.; Friel, E.; Suntzeff, N.B.

1986-02-01

A survey of subdwarf selected from the lists by Sandage (1964, 1969, 1982) was carried out with the 3 m telescope at Lick Observatory, using the image dissector scanner IDS as detector. The blue tube was used in order to obtain the NH band at lambda 3360 A and the CH band at lambda 4300 A. By comparing synthetic spectra with the observations, nitrogen and carbon abundances were derived for the sample of subdwarfs. They found that the nitrogen-to-carbon ratio is constant in time (or with metallicity) showing that nitrogen was produced as a primary element at early times. 16 references, 1 figure.

[Spatial characteristics of soil organic carbon and nitrogen storages in Songnen Plain maize belt].

Science.gov (United States)

Zhang, Chun-Hua; Wang, Zong-Ming; Ren, Chun-Ying; Song, Kai-Shan; Zhang, Bai; Liu, Dian-Wei

2010-03-01

By using the data of 382 typical soil profiles from the second soil survey at national and county levels, and in combining with 1:500000 digital soil maps, a spatial database of soil profiles was established. Based on this, the one meter depth soil organic carbon and nitrogen storage in Songnen Plain maize belt of China was estimated, with the spatial characteristics of the soil organic carbon and nitrogen densities as well as the relationships between the soil organic carbon and nitrogen densities and the soil types and land use types analyzed. The soil organic carbon and nitrogen storage in the maize belt was (163.12 +/- 26.48) Tg and (9.53 +/- 1.75) Tg, respectively, mainly concentrated in meadow soil, chernozem, and black soil. The soil organic carbon and nitrogen densities were 5.51-25.25 and 0.37-0.80 kg x m(-2), respectively, and the C/N ratio was about 7.90 -12.67. The eastern and northern parts of the belt had much higher carbon and nitrogen densities than the other parts of the belt, and upland soils had the highest organic carbon density [(19.07 +/- 2.44) kg x m(-2)], forest soils had the highest nitrogen density [(0.82 +/- 0.25) kg x m(-2)], while lowland soils had the lower organic carbon and nitrogen densities.

Post-fire redistribution of soil carbon and nitrogen at a grassland-shrubland ecotone

Science.gov (United States)

Wang, Guan; Li, Junran; Ravi, Sujith; Dukes, David; Gonzales, Howell B.; Sankey, Joel B.

2018-01-01

The rapid conversion of grasslands into shrublands has been observed in many arid and semiarid regions worldwide. Studies have shown that fire can provide certain forms of reversibility for shrub-grass transition due to resource homogenization and shrub mortality, especially in the early stages of shrub encroachment. Field-level post-fire soil resource redistribution has rarely been tested. Here we used prescribed fire in a shrubland-grassland transition zone in the northern Chihuahuan Desert to test the hypothesis that fire facilitates the remobilization of nutrient-enriched soil from shrub microsites to grass and bare microsites and thereby reduces the spatial heterogeneity of soil resources. Results show that the shrub microsites had the lowest water content compared to grass and bare microsites after fire, even when rain events occurred. Significant differences of total soil carbon (TC) and total soil nitrogen (TN) among the three microsites disappeared one year after the fire. The spatial autocorrelation distance increased from 1~2 m, approximately the mean size of an individual shrub canopy, to over 5 m one year after the fire for TC and TN. Patches of high soil C and N decomposed one year after the prescribed fire. Overall, fire stimulates the transfer of soil C and N from shrub microsites to nutrient-depleted grass and bare microsites. Such a redistribution of soil C and N, coupled with the reduced soil water content under the shrub canopies, suggests that fire might influence the competition between shrubs and grasses, leading to a higher grass, compared to shrub, coverage in this ecotone.

Nitrogen doped carbon nanotubes : synthesis, characterization and catalysis

NARCIS (Netherlands)

van Dommele, S.

2008-01-01

Nitrogen containing Carbon Nanotubes (NCNT) have altered physical- and chemical properties with respect to polarity, conductivity and reactivity as compared to conventional carbon nanotubes (CNT) and have potential for use in electronic applications or catalysis. In this thesis the incorporation of

Nitrogen-doped carbon capsules via poly(ionic liquid)-based layer-by-layer assembly.

Science.gov (United States)

Zhao, Qiang; Fellinger, Tim-Patrick; Antonietti, Markus; Yuan, Jiayin

2012-07-13

Layer-by-layer (LbL) assembly technique is applied for the first time for the preparation of nitrogen-doped carbon capsules. This approach uses colloid silica as template and two polymeric deposition components, that is, poly(ammonium acrylate) and a poly (ionic liquid) poly(3-cyanomethyl-1-vinylimidazolium bromide), which acts as both the carbon precursor and nitrogen source. Nitrogen-doped carbon capsules are prepared successfully by polymer wrapping, subsequent carbonization and template removal. The as-synthesized carbon capsules contain ≈7 wt% of nitrogen and have a structured specific surface area of 423 m(2) g(-1). Their application as supercapacitor has been briefly introduced. This work proves that LbL assembly methodology is available for preparing carbon structures of complex morphology. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

Directory of Open Access Journals (Sweden)

L. Wang

2013-02-01

Full Text Available Seasonal and spatial variations in foliar nitrogen (N parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L., Douglas fir (Pseudotsuga menziesii (Mirb. Franco and Scots pine (Pinus sylvestris L. growing in Denmark, the Netherlands and Finland, respectively. The objectives were to investigate the distribution of N pools within the canopies of the different forests and to relate this distribution to factors and plant strategies controlling leaf development throughout the seasonal course of a vegetation period. Leaf N pools generally showed much higher seasonal and vertical variability in beech than in the coniferous canopies. However, also the two coniferous tree species behaved very differently with respect to peak summer canopy N content and N re-translocation efficiency, showing that generalisations on tree internal vs. ecosystem internal N cycling cannot be made on the basis of the leaf duration alone. During phases of intensive N turnover in spring and autumn, the NH₄⁺ concentration in beech leaves rose considerably, while fully developed green beech leaves had relatively low tissue NH₄⁺, similar to the steadily low levels in Douglas fir and, particularly, in Scots pine. The ratio between bulk foliar concentrations of NH₄⁺ and H⁺, which is an indicator of the NH₃ emission potential, reflected differences in foliage N concentration, with beech having the highest values followed by Douglas fir and Scots pine. Irrespectively of the leaf habit, i.e. deciduous versus evergreen, the majority of the canopy foliage N was retained within the trees. This was accomplished through an effective N re-translocation (beech, higher foliage longevity (fir or both (boreal pine forest. In combination with data from a literature review, a general relationship of decreasing N re

Nitrogen Alters Fungal Communities in Boreal Forest Soil: Implications for Carbon Cycling

Science.gov (United States)

Allison, S. D.; Treseder, K. K.

2005-12-01

One potential effect of climate change in high latitude ecosystems is to increase soil nutrient availability. In particular, greater nitrogen availability could impact decomposer communities and lead to altered rates of soil carbon cycling. Since fungi are the primary decomposers in many high-latitude ecosystems, we used molecular techniques and field surveys to test whether fungal communities and abundances differed in response to nitrogen fertilization in a boreal forest ecosystem. We predicted that fungi that degrade recalcitrant carbon would decline under nitrogen fertilization, while fungi that degrade labile carbon would increase, leading to no net change in rates of soil carbon mineralization. The molecular data showed that basidiomycete fungi dominate the active fungal community in both fertilized and unfertilized soils. However, we found that fertilization reduced peak mushroom biomass by 79%, although most of the responsive fungi were ectomycorrhizal and therefore their capacity to degrade soil carbon is uncertain. Fertilization increased the activity of the cellulose-degrading enzyme beta-glucosidase by 78%, while protease activity declined by 39% and polyphenol oxidase, a lignin-degrading enzyme, did not respond. Rates of soil respiration did not change in response to fertilization. These results suggest that increased nitrogen availability does alter the composition of the fungal community, and its potential to degrade different carbon compounds. However, these differences do not affect the total flux of CO2 from the soil, even though the contribution to CO2 respiration from different carbon pools may vary with fertilization. We conclude that in the short term, increased nitrogen availability due to climate warming or nitrogen deposition is more likely to alter the turnover of individual carbon pools rather than total carbon fluxes from the soil. Future work should determine if changes in fungal community structure and associated differences in

Nitrogen controls on ecosystem carbon sequestration: a model implementation and application to Saskatchewan, Canada

Science.gov (United States)

Liu, J.; Price, D.T.; Chen, J.M.

2005-01-01

A plant–soil nitrogen (N) cycling model was developed and incorporated into the Integrated BIosphere Simulator (IBIS) of Foley et al. [Foley, J.A., Prentice, I.C., Ramankutty, N., Levis, S., Pollard, D., Sitch, S., Haxeltine, A., 1996. An integrated biosphere model of land surface process, terrestrial carbon balance and vegetation dynamics. Global Biogeochem. Cycles 10, 603–628]. In the N-model, soil mineral N regulates ecosystem carbon (C) fluxes and ecosystem C:N ratios. Net primary productivity (NPP) is controlled by feedbacks from both leaf C:N and soil mineral N. Leaf C:N determines the foliar and canopy photosynthesis rates, while soil mineral N determines the N availability for plant growth and the efficiency of biomass construction. Nitrogen controls on the decomposition of soil organic matter (SOM) are implemented through N immobilization and mineralization separately. The model allows greater SOM mineralization at lower mineral N, and conversely, allows greater N immobilization at higher mineral N. The model's seasonal and inter-annual behaviours are demonstrated. A regional simulation for Saskatchewan, Canada, was performed for the period 1851–2000 at a 10 km × 10 km resolution. Simulated NPP was compared with high-resolution (1 km × 1 km) NPP estimated from remote sensing data using the boreal ecosystem productivity simulator (BEPS) [Liu, J., Chen, J.M., Cihlar, J., Park, W.M., 1997. A process-based boreal ecosystem productivity simulator using remote sensing inputs. Remote Sens. Environ. 44, 81–87]. The agreement between IBIS and BEPS, particularly in NPP spatial variation, was considerably improved when the N controls were introduced into IBIS.

Canopy Photosynthesis: From Basics to Applications

NARCIS (Netherlands)

Hikosaka, Kouki; Niinemets, Ülo; Anten, N.P.R.

2016-01-01

A plant canopy, a collection of leaves, is an ecosystem-level unit of photosynthesis that assimilates carbon dioxide and exchanges other gases and energy with the atmosphere in a manner highly sensitive to ambient conditions including atmospheric carbon dioxide and water vapor concentrations, light

Carbon And Nitrogen Requirements For The Cultivation Of Oyster ...

African Journals Online (AJOL)

Carbon And Nitrogen Requirements For The Cultivation Of Oyster Mushroom ... It was found that under these experimental conditions, the carbon compounds supported growth except ribose, starch and dextrin. ... HOW TO USE AJOL.

Integrating terrestrial through aquatic processing of water, carbon and nitrogen over hot, cold and lukewarm moments in mixed land use catchments

Science.gov (United States)

Band, L. E.; Lin, L.; Duncan, J. M.

2017-12-01

A major challenge in understanding and managing freshwater volumes and quality in mixed land use catchments is the detailed heterogeneity of topography, soils, canopy, and inputs of water and biogeochemicals. The short space and time scale dynamics of sources, transport and processing of water, carbon and nitrogen in natural and built environments can have a strong influence on the timing and magnitude of watershed runoff and nutrient production, ecosystem cycling and export. Hydroclimate variability induces a functional interchange of terrestrial and aquatic environments across their transition zone with the temporal and spatial expansion and contraction of soil wetness, standing and flowing water over seasonal, diurnal and storm event time scales. Variation in sources and retention of nutrients at these scales need to be understood and represented to design optimal mitigation strategies. This paper discusses the conceptual framework used to design both simulation and measurement approaches, and explores these dynamics using an integrated terrestrial-aquatic watershed model of coupled water-carbon-nitrogen processes at resolutions necessary to resolve "hot spot/hot moment" phenomena in two well studied catchments in Long Term Ecological Research sites. The potential utility of this approach for design and assessment of urban green infrastructure and stream restoration strategies is illustrated.

Nitrogen deposition, land cover conversion, and contemporary carbon balance of Europe

Science.gov (United States)

Churkina, G.; Zaehle, S.; Hughes, J.; Viovy, N.; Jung, M.; Chen, Y.; Heimann, M.; Roedenbeck, C.; Jones, C.

2009-04-01

In Europe, atmospheric nitrogen deposition has more than doubled, forest cover was steadily increasing, and agricultural area was declining over the last 50 years. What effect have these changes had on the European carbon balance? In this study we estimate responses of the European land ecosystems to nitrogen deposition, land cover conversion and climate. We use results from four ecosystem process models such as BIOME-BGC, JULES, ORCHIDEE, and ORCHIDEE-CN to address this question. We discuss to which degree carbon balance of Europe has been altered by nitrogen deposition in comparison to other drivers and identify areas which carbon balance has been most effected by anthropogenic changes.

Climate-mediated nitrogen and carbon dynamics in a tropical watershed

Science.gov (United States)

Ballantyne, A. P.; Baker, P. A.; Fritz, S. C.; Poulter, B.

2011-06-01

Climate variability affects the capacity of the biosphere to assimilate and store important elements, such as nitrogen and carbon. Here we present biogeochemical evidence from the sediments of tropical Lake Titicaca indicating that large hydrologic changes in response to global glacial cycles during the Quaternary were accompanied by major shifts in ecosystem state. During prolonged glacial intervals, lake level was high and the lake was in a stable nitrogen-limited state. In contrast, during warm dry interglacials lake level fell and rates of nitrogen concentrations increased by a factor of 4-12, resulting in a fivefold to 24-fold increase in organic carbon concentrations in the sediments due to increased primary productivity. Observed periods of increased primary productivity were also associated with an apparent increase in denitrification. However, the net accumulation of nitrogen during interglacial intervals indicates that increased nitrogen supply exceeded nitrogen losses due to denitrification, thereby causing increases in primary productivity. Although primary productivity in tropical ecosystems, especially freshwater ecosystems, tends to be nitrogen limited, our results indicate that climate variability may lead to changes in nitrogen availability and thus changes in primary productivity. Therefore some tropical ecosystems may shift between a stable state of nitrogen limitation and a stable state of nitrogen saturation in response to varying climatic conditions.

Eco-Friendly Synthesis of Nitrogen-Doped Mesoporous Carbon for Supercapacitor Application

Directory of Open Access Journals (Sweden)

Georges Moussa

2018-03-01

Full Text Available A sustainable and simple synthesis procedure involving the co-assembly of green phenolic resin and amphiphilic polymer template in water/ethanol mixture at room temperature to synthesize nitrogen doped mesoporous carbon is reported herein. Guanine is proposed as a novel nitrogen-based precursor which is able to create H-bondings both with the phenolic resin and the template allowing the formation of mesoporous carbons with nitrogen atoms uniformly distributed in their framework. The influence of the synthesis procedure, template amount and annealing temperature on the carbon textural properties, structure and surface chemistry were investigated. For several conditions, carbon materials with ordered pore size and high nitrogen content (up to 10.6 at % could be achieved. The phase separation procedure combined with optimal amount of template favor the formation of ordered mesoporous carbons with higher specific surface area while the increase in the temperature induces a decrease in the surface area and amount of heteroatoms (N and O. The electrochemical performances as electrode in supercapacitors were evaluated in acidic medium and the capacitance was closely related to the material conductivity and surface chemistry.

MIL-100 derived nitrogen-embodied carbon shells embedded with iron nanoparticles

Science.gov (United States)

Mao, Chengyu; Kong, Aiguo; Wang, Yuan; Bu, Xianhui; Feng, Pingyun

2015-06-01

The use of metal-organic frameworks (MOFs) as templates and precursors to synthesize new carbon materials with controllable morphology and pre-selected heteroatom doping holds promise for applications as efficient non-precious metal catalysts. Here, we report a facile pyrolysis pathway to convert MIL-100 into nitrogen-doped carbon shells encapsulating Fe nanoparticles in a comparative study involving multiple selected nitrogen sources. The hierarchical porous architecture, embedded Fe nanoparticles, and nitrogen decoration endow this composite with a superior oxygen reduction activity. Furthermore, the excellent durability and high methanol tolerance even outperform the commercial Pt-C catalyst.The use of metal-organic frameworks (MOFs) as templates and precursors to synthesize new carbon materials with controllable morphology and pre-selected heteroatom doping holds promise for applications as efficient non-precious metal catalysts. Here, we report a facile pyrolysis pathway to convert MIL-100 into nitrogen-doped carbon shells encapsulating Fe nanoparticles in a comparative study involving multiple selected nitrogen sources. The hierarchical porous architecture, embedded Fe nanoparticles, and nitrogen decoration endow this composite with a superior oxygen reduction activity. Furthermore, the excellent durability and high methanol tolerance even outperform the commercial Pt-C catalyst. Electronic supplementary information (ESI) available: Material synthesis and elemental analysis, electrochemistry measurements, and additional figures. See DOI: 10.1039/c5nr02346g

Organic carbon, nitrogen and phosphorus contents of some soils of kaliti tea-estate, Bangladesh

International Nuclear Information System (INIS)

Ahmed, M. S.; Shahin, M. M. H.; Sanaullah, A. F. M.

2005-01-01

Some soil samples were collected from Kaliti Tea-Estate of Moulvibazar district, Bangladesh. Total nitrogen, organic carbon, organic matter, carbon-nitrogen ratio and available phosphorus content of the collected soil samples of different depths and of different topographic positions have been determined. Total nitrogen was found 0.07 to 0.12 % organic carbon and organic matter content found to vary from 0.79 to 1.25 and 1.36 to 2.15 % respectively. Carbon-nitrogen ratio of these soils varied from 9.84 to 10.69, while available phosphorus content varied from 2.11 to 4.13 ppm. (author)

Controls on Biogeochemical Cycling of Nitrogen in Urban Ecosystems

Science.gov (United States)

Templer, P. H.; Hutyra, L.; Decina, S.; Rao, P.; Gately, C.

2017-12-01

Rates of atmospheric nitrogen deposition are declining across much of the United States and Europe, yet they remain substantially elevated by almost an order of magnitude over pre-industrial levels and occur as hot spots in urban areas. We measured atmospheric inputs of inorganic and organic nitrogen in multiple urban sites around the Boston Metropolitan area, finding that urban rates are substantially elevated compared to nearby rural areas, and that the range of these atmospheric inputs are as large as observed urban to rural gradients. Within the City of Boston, the variation in deposition fluxes can be explained by traffic intensity, vehicle emissions, and spring fertilizer additions. Throughfall inputs of nitrogen are approximately three times greater than bulk deposition inputs in the city, demonstrating that the urban canopy amplifies rates of nitrogen reaching the ground surface. Similar to many other metropolitan areas of the United States, the City of Boston has 25% canopy cover; however, 25% of this tree canopy is located above impervious pavement. Throughfall inputs that do not have soil below the canopy to retain excess nitrogen may lead to greater inputs of nitrogen into nearby waterways through runoff. Most measurement stations for atmospheric nitrogen deposition are intentionally located away from urban areas and point sources of pollution to capture regional trends. Our data show that a major consequence of this network design is that hotspots of nitrogen deposition and runoff into urban and coastal waterways is likely underestimated to a significant degree. A more complete determination of atmospheric nitrogen deposition and its fate in urban ecosystems is critical for closing regional nitrogen budgets and for improving our understanding of biogeochemical nitrogen cycling across multiple spatial scales.

Nanostructured nitrogen-doped mesoporous carbon derived from polyacrylonitrile for advanced lithium sulfur batteries

Energy Technology Data Exchange (ETDEWEB)

Liu, Ying; Zhao, Xiaohui; Chauhan, Ghanshyam S. [Department of Chemical Engineering and Research Institute for Green Energy Convergence Technology, Gyeongsang National University, 501 Jinju-daero, Jinju 660-701 (Korea, Republic of); Ahn, Jou-Hyeon, E-mail: jhahn@gnu.ac.kr [Department of Chemical Engineering and Research Institute for Green Energy Convergence Technology, Gyeongsang National University, 501 Jinju-daero, Jinju 660-701 (Korea, Republic of); Department of Materials Engineering and Convergence Technology and RIGET, Gyeongsang National University, 501 Jinju-daero, Jinju 660-701 (Korea, Republic of)

2016-09-01

Graphical abstract: Well-ordered nitrogen-doped mesoporous carbon materials were prepared by in-situ polymerization of polyacrylonitrile in SBA-15 template. The composite of sulfur and nitrogen-doped carbon was successfully used as a cathode material for lithium sulfur battery. - Highlights: • N-doped mesoporous carbons were prepared with PAN as carbon source. • Highly ordered pore system facilitates sulfur loading. • Ladder-type carbon matrix provides good structural stability for confining sulfur. • N-doping ensures an improved absorbability of soluble polysulfides. - Abstract: Nitrogen doping in carbon matrix can effectively improve the wettability of electrolyte and increase electric conductivity of carbon by ensuring fast transfer of ions. We synthesized a series of nitrogen-doped mesoporous carbons (CPANs) via in situ polymerization of polyacrylonitrile (PAN) in SBA-15 template followed by carbonization at different temperatures. Carbonization results in the formation of ladder structure which enhances the stability of the matrix. In this study, CPAN-800, carbon matrix synthesized by the carbonization at 800 °C, was found to possess many desirable properties such as high specific surface area and pore volume, moderate nitrogen content, and highly ordered mesoporous structure. Therefore, it was used to prepare S/CPAN-800 composite as cathode material in lithium sulfur (Li-S) batteries. The S/CPAN-800 composite was proved to be an excellent material for Li-S cells which delivered a high initial discharge capacity of 1585 mAh g{sup −1} and enhanced capacity retention of 862 mAh g{sup −1} at 0.1 C after 100 cycles.

Worldwide organic soil carbon and nitrogen data

Energy Technology Data Exchange (ETDEWEB)

Zinke, P.J.; Stangenberger, A.G. [Univ. of California, Berkeley, CA (United States). Dept. of Forestry and Resource Management; Post, W.M.; Emanual, W.R.; Olson, J.S. [Oak Ridge National Lab., TN (United States)

1986-09-01

The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.

Developing Ecological Models on Carbon and Nitrogen in Secondary Facultative Ponds

Directory of Open Access Journals (Sweden)

Aponte-Reyes Alexander

2014-07-01

Full Text Available Ecological models formulated for TOC, CO2, NH4+, NO3- and NTK, based in literature reviewed and field work were obtained monitoring three facultative secondary stabilization ponds, FSSP, pilots: conventional pond, CP, baffled pond, BP, and baffled-meshed pond, BMP. Models were sensitive to flow inlet, solar radiation, pH and oxygen content; the sensitive parameters in Carbon Model were KCOT Ba, umax Ba, umax Al, K1OX, VAl, R1DCH4, YBh. The sensitive parameters in the Nitrogen model were KCOT Ba, umax Ba, umax Al, VAl, KOPH, KOPA, r4An. The test t–paired showed a good simulating of Carbon model refers to TOC in FSSP; on the other side, the Nitrogen model showed a good simulating of NH4+. Different topological models modify ecosystem ecology forcing different transformation pathways of Nitrogen; equal transformations of the Carbon BMP topology could be achieved using lower volumes, however, a calibration for a new model would be required. Carbon and Nitrogen models developed could be coupled to hydrodynamics models for better modeling of FSSP.

Abundances in field dwarf stars. II. Carbon and nitrogen abundances

Energy Technology Data Exchange (ETDEWEB)

Laird, J.B.

1985-02-15

Intermediate-dispersion spectra of 116 field dwarf stars, plus 10 faint field giants and 3 Hyades dwarfs, have been used to derive carbon and nitrogen abundances relative to iron. The program sample includes both disk and halo stars, spanning a range in (Fe/H) of +0.50 to -2.45. Synthetic spectra of CH and NH bands have been used to determine carbon and nitrogen abundances. The C/Fe ratio is solar over the range of metallicity studied, with an estimated intrinsic scatter of 0.10 dex. Down to (Fe/H)roughly-equal-1.8, below which the nitrogen abundance could not be measured, the N/Fe ratio is also constant for the majority of stars, indicating that nitrogen production is largely primary. Four halo stars are found to be enhanced in nitrogen relative to iron, by factors between 5 and 50, although their carbon abundances appear to be normal. These results are discussed in connection with the chemical evolution of the Galaxy and the sites of C, N, and Fe nucleosynthesis. The results require that C, N, and Fe be produced in stars of similar mass. Our current understanding of N production, then, implies that most Type I supernovae have intermediate-mass progenitors. The nitrogen in the N-enhanced halo stars is very probably primordial, indicating that the interstellar medium at early epochs contained substantial inhomogeneities.

Abundances in field dwarf stars. II. Carbon and nitrogen abundances

International Nuclear Information System (INIS)

Laird, J.B.

1985-01-01

Intermediate-dispersion spectra of 116 field dwarf stars, plus 10 faint field giants and 3 Hyades dwarfs, have been used to derive carbon and nitrogen abundances relative to iron. The program sample includes both disk and halo stars, spanning a range in [Fe/H] of +0.50 to -2.45. Synthetic spectra of CH and NH bands have been used to determine carbon and nitrogen abundances. The C/Fe ratio is solar over the range of metallicity studied, with an estimated intrinsic scatter of 0.10 dex. Down to [Fe/H]roughly-equal-1.8, below which the nitrogen abundance could not be measured, the N/Fe ratio is also constant for the majority of stars, indicating that nitrogen production is largely primary. Four halo stars are found to be enhanced in nitrogen relative to iron, by factors between 5 and 50, although their carbon abundances appear to be normal. These results are discussed in connection with the chemical evolution of the Galaxy and the sites of C, N, and Fe nucleosynthesis. The results require that C, N, and Fe be produced in stars of similar mass. Our current understanding of N production, then, implies that most Type I supernovae have intermediate-mass progenitors. The nitrogen in the N-enhanced halo stars is very probably primordial, indicating that the interstellar medium at early epochs contained substantial inhomogeneities

Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity

Science.gov (United States)

Pellegrini, Adam F. A.; Ahlström, Anders; Hobbie, Sarah E.; Reich, Peter B.; Nieradzik, Lars P.; Staver, A. Carla; Scharenbroch, Bryant C.; Jumpponen, Ari; Anderegg, William R. L.; Randerson, James T.; Jackson, Robert B.

2018-01-01

Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.

[Active crop canopy sensor-based nitrogen diagnosis for potato].

Science.gov (United States)

Yu, Jing; Li, Fei; Qin, Yong-Lin; Fan, Ming-Shou

2013-11-01

In the present study, two potato experiments involving different N rates in 2011 were conducted in Wuchuan County and Linxi County, Inner Mongolia. Normalized difference vegetation index (NDVI) was collected by an active GreenSeeker crop canopy sensor to estimate N status of potato. The results show that the NDVI readings were poorly correlated with N nutrient indicators of potato at vegetative Growth stage due to the influence of soil background. With the advance of growth stages, NDVI values were exponentially related to plant N uptake (R2 = 0.665) before tuber bulking stage and were linearly related to plant N concentration (R2 = 0.699) when plant fully covered soil. In conclusion, GreenSeeker active crop sensor is a promising tool to estimate N status for potato plants. The findings from this study may be useful for developing N recommendation method based on active crop canopy sensor.

Effects of wetland recovery on soil labile carbon and nitrogen in the Sanjiang Plain.

Science.gov (United States)

Huang, Jingyu; Song, Changchun; Nkrumah, Philip Nti

2013-07-01

Soil management significantly affects the soil labile organic factors. Understanding carbon and nitrogen dynamics is extremely helpful in conducting research on active carbon and nitrogen components for different kinds of soil management. In this paper, we examined the changes in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) to assess the effect and mechanisms of land types, organic input, soil respiration, microbial species, and vegetation recovery under Deyeuxia angustifolia freshwater marshes (DAMs) and recovered freshwater marsh (RFM) in the Sanjiang Plain, Northeast China. Identifying the relationship among the dynamics of labile carbon, nitrogen, and soil qualification mechanism using different land management practices is therefore important. Cultivation and land use affect intensely the DOC, DON, MBC, and MBN in the soil. After DAM soil tillage, the DOC, DON, MBC, and MBN at the surface of the agricultural soil layer declined significantly. In contrast, their recovery was significant in the RFM surface soil. A long time was needed for the concentration of cultivated soil total organic carbon and total nitrogen to be restored to the wetland level. The labile carbon and nitrogen fractions can reach a level similar to that of the wetland within a short time. Typical wetland ecosystem signs, such as vegetation, microbes, and animals, can be recovered by soil labile carbon and nitrogen fraction restoration. In this paper, the D. angustifolia biomass attained natural wetland level after 8 years, indicating that wetland soil labile fractions can support wetland eco-function in a short period of time (4 to 8 years) for reconstructed wetland under suitable environmental conditions.

Nitrogen-containing hydrothermal carbons with superior performance in supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Zhao, Li [Colloid Chemistry Department, Max-Planck Institute for Colloids and Interfaces, Am Muehlenberg 1, 14424 Potsdam (Germany); Institute of Coal Chemistry, Chinese Academy of Sciences, 27th Taoyuan South Road, 030001 Taiyuan (China); Fan, Li-Zhen; Zhou, Meng-Qi; Guan, Hui; Qiao, Suyan [School of Materials Science and Engineering, University of Science and Technology Beijing, 100083 Beijing (China); Antonietti, Markus; Titirici, Maria-Magdalena [Colloid Chemistry Department, Max-Planck Institute for Colloids and Interfaces, Am Muehlenberg 1, 14424 Potsdam (Germany)

2010-12-01

Microporous nitrogen-doped carbons produced by hydrothermal carbonization of biomass derivative followed by chemical activation showed excellent supercapacitive capacitance performance both in acid and base electrolytes. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Stable carbon and nitrogen isotopes in vertical peat profiles of natural and drained boreal peatlands

Science.gov (United States)

Nykänen, Hannu; Mpamah, Promise; Rissanen, Antti; Pitkänen, Aki; Turunen, Jukka; Simola, Heikki

2015-04-01

Peatlands form a significant carbon pool in the global carbon cycle. Change in peat hydrology, due to global warming is projected to change microbiological processes and peat carbon pool. We tested if bulk stable carbon and nitrogen isotopes serve as indicators of severe long term drying in peatlands drained for forestry. Depth profile analysis of peat, for their carbon and nitrogen content as well as their carbon and nitrogen stable isotopic signatures, were conducted for peatlands in southern and eastern Finland, having ombrotrophic and minerotrophic natural and corresponding drained pairs or separate drained sites. The selection of sites allowed us to compare changes due to different fertility and changes due to long term artificial drying. Drainage lasting over 40 years has led to changes in hydrology, vegetation, nutrient mineralization and respiration. Furthermore, increased nutrient uptake and possible recycling of peat nitrogen and carbon trough vegetation back to the peat surface, also possibly has an effect on the stable isotopic composition of peat carbon and nitrogen. We think that drainage induced changes somehow correspond to those caused by changed hydrology due to climate change. We will present data from these measurements and discuss their implications for carbon and nitrogen flows in peatlands.

A Natural Light/Dark Cycle Regulation of Carbon-Nitrogen Metabolism and Gene Expression in Rice Shoots.

Science.gov (United States)

Li, Haixing; Liang, Zhijun; Ding, Guangda; Shi, Lei; Xu, Fangsen; Cai, Hongmei

2016-01-01

Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites, and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate, and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism, and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention, and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799) were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant growth and

A natural light/dark cycle regulation of carbon-nitrogen metabolism and gene expression in rice shoots

Directory of Open Access Journals (Sweden)

Haixing Li

2016-08-01

Full Text Available Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00 and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799 were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant

Emissions of carbon, nitrogen, and sulfur from biomass burning in Nigeria

International Nuclear Information System (INIS)

Akeredolu, F.; Isichei, A.O.

1991-01-01

The atmospheric implications of the effects of burning of vegetation in Nigeria are discussed. The following topics are explored: the extent of biomass burning by geographical area; estimates of emission rates of carbon, nitrogen and sulfur; and the impact on biogeochemical cycling of elements. The results suggest that biomass burning generates a measurable impact on the cycling of carbon and nitrogen

Stable carbon, oxygen, and nitrogen, isotope analysis of plants from a South Asian tropical forest: Implications for primatology.

Science.gov (United States)

Roberts, Patrick; Blumenthal, Scott A; Dittus, Wolfgang; Wedage, Oshan; Lee-Thorp, Julia A

2017-06-01

Stable isotope analysis of primate tissues in tropical forest contexts is an increasingly popular means of obtaining information about niche distinctions among sympatric species, including preferences in feeding height, forest canopy density, plant parts, and trophism. However, issues of equifinality mean that feeding height, canopy density, as well as the plant parts and plant species consumed, may produce similar or confounding effects. With a few exceptions, researchers have so far relied largely on general principles and/or limited plant data from the study area as references for deducing the predominant drivers of primate isotope variation. Here, we explore variation in the stable carbon (δ 13 C), nitrogen (δ 15 N), and oxygen (δ 18 O) isotope ratios of 288 plant samples identified as important to the three primate species from the Polonnaruwa Nature Sanctuary, Sri Lanka, relative to plant part, season, and canopy height. Our results show that plant part and height have the greatest effect on the δ 13 C and δ 18 O measurements of plants of immediate relevance to the primates, Macaca sinica, Semnopithecus priam thersites, and Trachypithecus vetulus, living in this monsoonal tropical forest. We find no influence of plant part, height or season on the δ 15 N of measured plants. While the plant part effect is particularly pronounced in δ 13 C between fruits and leaves, differential feeding height, and plant taxonomy influence plant δ 13 C and δ 18 O differences in addition to plant organ. Given that species composition in different regions and forest types will differ, the results urge caution in extrapolating general isotopic trends without substantial local baselines studies. © 2017 Wiley Periodicals, Inc.

Hierarchical porous nitrogen-doped partial graphitized carbon monoliths for supercapacitor

Energy Technology Data Exchange (ETDEWEB)

Yu, Yifeng; Du, Juan; Liu, Lei; Wang, Guoxu; Zhang, Hongliang; Chen, Aibing, E-mail: chen-ab@163.com [Hebei University of Science and Technology, College of Chemical and Pharmaceutical Engineering (China)

2017-03-15

Porous carbon monoliths have attracted great interest in many fields due to their easy availability, large specific surface area, desirable electronic conductivity, and tunable pore structure. In this work, hierarchical porous nitrogen-doped partial graphitized carbon monoliths (N–MC–Fe) with ordered mesoporous have been successfully synthesized by using resorcinol-formaldehyde as precursors, iron salts as catalyst, and mixed triblock copolymers as templates via a one-step hydrothermal method. In the reactant system, hexamethylenetetramine (HMT) is used as nitrogen source and one of the carbon precursors under hydrothermal conditions instead of using toxic formaldehyde. The N–MC–Fe show hierarchically porous structures, with interconnected macroporous and ordered hexagonally arranged mesoporous. Nitrogen element is in situ doped into carbon through decomposition of HMT. Iron catalyst is helpful to improve the graphitization degree and pore volume of N–MC–Fe. The synthesis strategy is user-friendly, cost-effective, and can be easily scaled up for production. As supercapacitors, the N–MC–Fe show good capacity with high specific capacitance and good electrochemical stability.

Carbon and nitrogen translocation between seagrass ramets

NARCIS (Netherlands)

Marbà, N.; Hemminga, M.A.; Mateo, M.A.; Duarte, C.M.; Maas, Y.E.M.; Terrados, J.; Gacia, E.

2002-01-01

The spatial scale and the magnitude of carbon and nitrogen translocation was examined in 5 tropical (Cymodocea serrulata, Halophila stipulacea, Halodule uninervis, Thalassodendron ciliatum, Thalassia hemprichii) and 3 temperate (Cymodocea nodosa, Posidonia oceanica, Zostera noltii) seagrass species

Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources.

Science.gov (United States)

Wang, Ping; Zhang, Geng; Li, Zhichen; Sheng, Wangjian; Zhang, Yichi; Gu, Jiangjiang; Zheng, Xinsheng; Cao, Feifei

2016-10-03

Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO 4 to obtain LiFePO 4 @nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO 4 particles can effectively enhance the electrical conductivity and provide fast Li + transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO 4 ) exhibits a favorable rate performance and stable cycling performance.

Utilization of carbon and nitrogen sources by Streptomyces ...

African Journals Online (AJOL)

We tested a number of carbon and nitrogen compounds for their effect on the production of an antibacterial antibiotic by Streptomyces kananmyceticus M27. Dextrose was found to be the most suitable carbon source, though maltose, sucrose, and soluble starch gave moderate yields. (NH4)H2PO4 and yeast extract were ...

[Interactions of straw, nitrogen fertilizer and bacterivorous nematodes on soil labile carbon and nitrogen and greenhouse gas emissions].

Science.gov (United States)

Zhang, Teng-Hao; Wang, Nan; Liu, Man-Qiang; Li, Fang-Hui; Zhu, Kang-Li; Li, Hui-Xin; Hu, Feng

2014-11-01

A 3 x 2 factorial design of microcosm experiment was conducted to investigate the interactive effects of straw, nitrogen fertilizer and bacterivorous nematodes on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), dissolved organic carbon (DOC) and nitrogen (DON), mineral nitrogen (NH(4+)-N and NO(3-)-N), and greenhouse gas (CO2, N2O and CH4) emissions. Results showed that straw amendment remarkably increased the numbers of bacterivorous nematodes and the contents of Cmic and Nmic, but Cmic and Nmic decreased with the increasing dose of nitrogen fertilization. The effects of bacterivorous nematodes strongly depended on either straw or nitrogen fertilization. The interactions of straw, nitrogen fertilization and bacterivorous nematodes on soil DOC, DON and mineral nitrogen were strong. Straw and nitrogen fertilization increased DOC and mineral nitrogen contents, but their influences on DON depended on the bacterivorous nematodes. The DOC and mineral nitrogen were negatively and positively influenced by the bacterivorous nematodes, re- spectively. Straw significantly promoted CO2 and N2O emissions but inhibited CH4 emission, while interactions between nematodes and nitrogen fertilization on emissions of greenhouse gases were obvious. In the presence of straw, nematodes increased cumulative CO2 emissions with low nitrogen fertilization, but decreased CO2 and N2O emissions with high nitrogen fertilization on the 56th day after incubation. In summary, mechanical understanding the soil ecological process would inevitably needs to consider the roles of soil microfauna.

Age-related effects on leaf area/sapwood area relationships, canopy transpiration and carbon gain of Norway spruce stands (Picea abies) in the Fichtelgebirge, Germany.

Science.gov (United States)

Köstner, B; Falge, E; Tenhunen, J D

2002-06-01

Stand age is an important structural determinant of canopy transpiration (E(c)) and carbon gain. Another more functional parameter of forest structure is the leaf area/sapwood area relationship, A(L)/A(S), which changes with site conditions and has been used to estimate leaf area index of forest canopies. The interpretation of age-related changes in A(L)/A(S) and the question of how A(L)/A(S) is related to forest functions are of current interest because they may help to explain forest canopy fluxes and growth. We conducted studies in mature stands of Picea abies (L.) Karst. varying in age from 40 to 140 years, in tree density from 1680 to 320 trees ha(-1), and in tree height from 15 to 30 m. Structural parameters were measured by biomass harvests of individual trees and stand biometry. We estimated E(c) from scaled-up xylem sap flux of trees, and canopy-level fluxes were predicted by a three-dimensional microclimate and gas exchange model (STANDFLUX). In contrast to pine species, A(L)/A(S) of P. abies increased with stand age from 0.26 to 0.48 m(2) cm(-2). Agreement between E(c) derived from scaled-up sap flux and modeled canopy transpiration was obtained with the same parameterization of needle physiology independent of stand age. Reduced light interception per leaf area and, as a consequence, reductions in net canopy photosynthesis (A(c)), canopy conductance (g(c)) and E(c) were predicted by the model in the older stands. Seasonal water-use efficiency (WUE = A(c)/E(c)), derived from scaled-up sap flux and stem growth as well as from model simulation, declined with increasing A(L)/A(S) and stand age. Based on the different behavior of age-related A(L)/A(S) in Norway spruce stands compared with other tree species, we conclude that WUE rather than A(L)/A(S) could represent a common age-related property of all species. We also conclude that, in addition to hydraulic limitations reducing carbon gain in old stands, a functional change in A(L)/A(S) that is related to

40 CFR 89.112 - Oxides of nitrogen, carbon monoxide, hydrocarbon, and particulate matter exhaust emission standards.

Science.gov (United States)

2010-07-01

....112 Oxides of nitrogen, carbon monoxide, hydrocarbon, and particulate matter exhaust emission... emissions of oxides of nitrogen, carbon monoxide, hydrocarbon, and nonmethane hydrocarbon are measured using... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Oxides of nitrogen, carbon monoxide...

Effects of nitrogen application rate and leaf age on the distribution pattern of leaf SPAD readings in the rice canopy.

Directory of Open Access Journals (Sweden)

Hu Yang

Full Text Available A Soil-Plant Analysis Development (SPAD chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008-2009 using rice plants treated with six different N application levels. N distribution pattern was determined by SPAD readings based on the temporal dynamics of N concentrations in individual leaves. At 62 days after transplantation (DAT in 2008 and DAT 60 in 2009, leaf SPAD readings increased from the upper to lower in the rice canopy that received N levels of 150 to 375 kg ha(-1The differences in SPAD readings between the upper and lower leaf were larger under higher N application rates. However, as plants grew, this atypical distribution of SPAD readings in canopy leaf quickly reversed to the general order. In addition, temporal dynamics of the leaf SPAD readings (N concentrations were fitted to a piecewise function. In our model, changes in leaf SPAD readings were divided into three stages: growth, functioning, and senescence periods. The leaf growth period lasted approximately 6 days, and cumulative growing days were not affected by N application rates. The leaf functioning period was represented with a relatively stable SPAD reading related to N application rate, and cumulative growing days were extended with increasing N application rates. A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period. The rate of decrease in SPAD readings increased with the age of leaves, but the rate was slowed by N application. As leaves in the lower canopy were physiologically older than leaves in the upper canopy, the rate of decrease in SPAD readings was faster in the lower leaves.

Effects of diffuse radiation on canopy gas exchange processes in a forest ecosystem

Science.gov (United States)

Knohl, Alexander; Baldocchi, Dennis D.

2008-06-01

Forest ecosystems across the globe show an increase in ecosystem carbon uptake efficiency under conditions with high fraction of diffuse radiation. Here, we combine eddy covariance flux measurements at a deciduous temperate forest in central Germany with canopy-scale modeling using the biophysical multilayer model CANVEG to investigate the impact of diffuse radiation on various canopy gas exchange processes and to elucidate the underlying mechanisms. Increasing diffuse radiation enhances canopy photosynthesis by redistributing the solar radiation load from light saturated sunlit leaves to nonsaturated shade leaves. Interactions with atmospheric vapor pressure deficit and reduced leaf respiration are only of minor importance to canopy photosynthesis. The response strength of carbon uptake to diffuse radiation depends on canopy characteristics such as leaf area index and leaf optical properties. Our model computations shows that both canopy photosynthesis and transpiration increase initially with diffuse fraction, but decrease after an optimum at a diffuse fraction of 0.45 due to reduction in global radiation. The initial increase in canopy photosynthesis exceeds the increase in transpiration, leading to a rise in water-use-efficiency. Our model predicts an increase in carbon isotope discrimination with water-use-efficiency resulting from differences in the leaf-to-air vapor pressure gradient and atmospheric vapor pressure deficit. This finding is in contrast to those predicted with simple big-leaf models that do not explicitly calculate leaf energy balance. At an annual scale, we estimate a decrease in annual carbon uptake for a potential increase in diffuse fraction, since diffuse fraction was beyond the optimum for 61% of the data.

Stomatal Conductance, Plant Hydraulics, and Multilayer Canopies: A New Paradigm for Earth System Models or Unnecessary Uncertainty

Science.gov (United States)

Bonan, G. B.

2016-12-01

Soil moisture stress is a key regulator of canopy transpiration, the surface energy budget, and land-atmosphere coupling. Many land surface models used in Earth system models have an ad-hoc parameterization of soil moisture stress that decreases stomatal conductance with soil drying. Parameterization of soil moisture stress from more fundamental principles of plant hydrodynamics is a key research frontier for land surface models. While the biophysical and physiological foundations of such parameterizations are well-known, their best implementation in land surface models is less clear. Land surface models utilize a big-leaf canopy parameterization (or two big-leaves to represent the sunlit and shaded canopy) without vertical gradients in the canopy. However, there are strong biometeorological and physiological gradients in plant canopies. Are these gradients necessary to resolve? Here, I describe a vertically-resolved, multilayer canopy model that calculates leaf temperature and energy fluxes, photosynthesis, stomatal conductance, and leaf water potential at each level in the canopy. In this model, midday leaf water stress manifests in the upper canopy layers, which receive high amounts of solar radiation, have high leaf nitrogen and photosynthetic capacity, and have high stomatal conductance and transpiration rates (in the absence of leaf water stress). Lower levels in the canopy become water stressed in response to longer-term soil moisture drying. I examine the role of vertical gradients in the canopy microclimate (solar radiation, air temperature, vapor pressure, wind speed), structure (leaf area density), and physiology (leaf nitrogen, photosynthetic capacity, stomatal conductance) in determining above canopy fluxes and gradients of transpiration and leaf water potential within the canopy.

Stable carbon, nitrogen and sulfur isotopes in non-carbonate fractions of cold-seep carbonates

Science.gov (United States)

Feng, Dong; Peng, Yongbo; Peckmann, Jörn; Roberts, Harry; Chen, Duofu

2017-04-01

Sulfate-driven anaerobic oxidation of methane (AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. This process promotes the formation of carbonates close to the seafloor along continental margins. The geochemical characteristics of the carbonate minerals of these rocks are increasingly understood, questions remain about the geochemical characteristics of the non-carbonate fractions. Here, we report stable carbon, nitrogen and sulfur isotope patterns in non-carbonate fractions of seep carbonates. The authigenic carbonates were collected from three modern seep provinces (Black Sea, Gulf of Mexico, and South China Sea) and three ancient seep deposits (Marmorito, northern Italy, Miocene; SR4 deposit of the Lincoln Creek Formation and Whiskey Creek, western Washington, USA, Eocene to Oligocene). The δ13C values of non-carbonate fractions range from ˜-25‰ to -80‰ VPDB. These values indicate that fossil methane mixed with varying amounts of pelagic organic matter is the dominant source of carbon in these fractions. The relatively small offset between the δ34S signatures of the non-carbonate fractions and the respective sulfide minerals suggests that locally produced hydrogen sulfide is the main source of sulfur in seep environments. The δ15N values of the non-carbonate fractions are generally lower than the corresponding values of deep-sea sediments, suggesting that organic nitrogen is mostly of a local origin. This study reveals the potential of using δ13C, δ15N, δ34S values to discern seep and non-seep deposits. In cases where δ13Ccarbonate values are only moderately low due to mixing processes and lipid biomarkers have been erased in the course of burial, it is difficult to trace back AOM owing to the lack of other records. This problem is even more pronounced when authigenic carbonate is not available in ancient seep environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support

Temporal Variability of Canopy Light Use Efficiency and its Environmental Controls in a Subtropical Mangrove Wetland

Science.gov (United States)

Zhu, X.

2016-12-01

Mangrove wetlands play an important role in global carbon cycle due to their strong carbon sequestration resulting from high plant carbon assimilation and low soil respiration. However, temporal variability of carbon sequestration in mangrove wetlands is less understood since carbon processes of mangrove wetlands are influenced by many complicated and concurrent environmental controls including tidal activities, site climate and soil conditions. Canopy light use efficiency (LUE), is the most important plant physiological parameter that can be used to describe the temporal dynamics of canopy photosynthesis, and therefore a better characterization of temporal variability of canopy LUE will improve our understanding in mangrove photosynthesis and carbon balance. One of our aims is to study the temporal variability of canopy LUE and its environmental controls in a subtropical mangrove wetland. Half-hourly canopy LUE is derived from eddy covariance (EC) carbon flux and photosynthesis active radiation observations, and half-hourly environmental controls we measure include temperature, humidity, precipitation, radiation, tidal height, salinity, etc. Another aim is to explore the links between canopy LUE and spectral indices derived from near-surface tower-based remote sensing (normalized difference vegetation index, enhanced vegetation index, photochemical reflectance index, solar-induced chlorophyll fluorescence, etc.), and then identify potential quantitative relationships for developing remote sensing-based estimation methods of canopy LUE. At present, some instruments in our in-situ observation system have not yet been installed (planned in next months) and therefore we don't have enough measurements to support our analysis. However, a preliminary analysis of our historical EC and climate observations in past several years indicates that canopy LUE shows strong temporal variability and is greatly affected by environmental factors such as tidal activity. Detailed and

Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

Science.gov (United States)

Wang, L.; Ibrom, A.; Korhonen, J. F. J.; Arnoud Frumau, K. F.; Wu, J.; Pihlatie, M.; Schjoerring, J. K.

2012-07-01

Seasonal and spatial variations in foliar nitrogen (N) parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L.), Douglas fir (Pseudotsuga menziesii, Mirb., Franco) and Scots pine (Pinus sylvestris L.) in Denmark, The Netherlands and Finland, respectively. This was done in order to obtain information about functional acclimation, tree internal N conservation and its relevance for both ecosystem internal N cycling and foliar N exchange with the atmosphere. Leaf N pools generally showed much higher seasonal variability in beech trees than in the coniferous canopies. The concentrations of N and chlorophyll in the beech leaves were synchronized with the seasonal course of solar radiation implying close physiological acclimation, which was not observed in the coniferous needles. During phases of intensive N metabolism in the beech leaves, the NH4+ concentration rose considerably. This was compensated for by a strong pH decrease resulting in relatively low Γ values (ratio between tissue NH4+ and H+). The Γ values in the coniferous were even smaller than in beech, indicating low probability of NH3 emissions from the foliage to the atmosphere as an N conserving mechanism. The reduction in foliage N content during senescence was interpreted as N re-translocation from the senescing leaves into the rest of the trees. The N re-translocation efficiency (ηr) ranged from 37 to 70% and decreased with the time necessary for full renewal of the canopy foliage. Comparison with literature data from in total 23 tree species showed a general tendency for ηr to on average be reduced by 8% per year the canopy stays longer, i.e. with each additional year it takes for canopy renewal. The boreal pine site returned the lowest amount of N via foliage litter to the soil, while the temperate Douglas fir stand which had the largest peak canopy N content and the lowestηr returned the highest amount of N to the soil. These results

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

Science.gov (United States)

Koven, Charles D.; Lawrence, David M.; Riley, William J.

2015-01-01

Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon−nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw. PMID:25775603

Remote sensing of LAI, chlorophyll and leaf nitrogen pools of crop- and grasslands in five European landscapes

DEFF Research Database (Denmark)

Bøgh, Eva; Houborg, R; Bienkowski, J

2013-01-01

Leaf nitrogen and leaf surface area influence the exchange of gases between terrestrial ecosystems and the atmosphere, and they play a significant role in the global cycles of carbon, nitrogen and water. Remote sensing data from satellites can be used to estimate leaf area index (LAI), leaf......). Predictabilities of SVIs and REGFLEC simulations generally improved when constrained to single land use categories (wheat, maize, barley, grass) across the European landscapes, reflecting sensitivity to canopy structures. Predictability further improved when constrained to local (10 × 10 km2) landscapes, thereby...

In Situ One-Step Synthesis of Hierarchical Nitrogen-Doped Porous Carbon for High Performance Supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Jeon, Ju Won [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Texas A & M Univ., College Station, TX (United States); Sharma, Ronish [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Meduri, Praveen [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Arey, Bruce W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schaef, Herbert T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lutkenhaus, Jodie [Texas A & M Univ., College Station, TX (United States); Lemmon, John P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thallapally, Praveen K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nandasiri, Manjula I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGrail, B. Peter [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nune, Satish K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2014-04-30

Electrochemical performance of the existing state-of-the art capacitors is not very high, key scientific barrier is that its charge storage mechanism wholly depends on adsorption of electrolyte on electrode. We present a novel method for the synthesis of nitrogen -doped porous carbons and address the drawback by precisely controlling composition and surface area. Nitrogen-doped porous carbon was synthesized using a self-sacrificial template technique without any additional nitrogen and carbon sources. They exhibited exceptionally high capacitance (239 Fg-1) due to additional pseudocapacitance originating from doped nitrogen. Cycling tests showed no obvious capacitance decay even after 10,000 cycles, which meets the requirement of commercial supercapacitors. Our method is simple and highly efficient for the production of large quantities of nitrogen-doped porous carbons.

Variation in foliar respiration and wood CO2 efflux rates among species and canopy layers in a wet tropical forest.

Science.gov (United States)

Asao, Shinichi; Bedoya-Arrieta, Ricardo; Ryan, Michael G

2015-02-01

As tropical forests respond to environmental change, autotrophic respiration may consume a greater proportion of carbon fixed in photosynthesis at the expense of growth, potentially turning the forests into a carbon source. Predicting such a response requires that we measure and place autotrophic respiration in a complete carbon budget, but extrapolating measurements of autotrophic respiration from chambers to ecosystem remains a challenge. High plant species diversity and complex canopy structure may cause respiration rates to vary and measurements that do not account for this complexity may introduce bias in extrapolation more detrimental than uncertainty. Using experimental plantations of four native tree species with two canopy layers, we examined whether species and canopy layers vary in foliar respiration and wood CO2 efflux and whether the variation relates to commonly used scalars of mass, nitrogen (N), photosynthetic capacity and wood size. Foliar respiration rate varied threefold between canopy layers, ∼0.74 μmol m(-2) s(-1) in the overstory and ∼0.25 μmol m(-2) s(-1) in the understory, but little among species. Leaf mass per area, N and photosynthetic capacity explained some of the variation, but height explained more. Chamber measurements of foliar respiration thus can be extrapolated to the canopy with rates and leaf area specific to each canopy layer or height class. If area-based rates are sampled across canopy layers, the area-based rate may be regressed against leaf mass per area to derive the slope (per mass rate) to extrapolate to the canopy using the total leaf mass. Wood CO2 efflux varied 1.0-1.6 μmol m(-2) s(-1) for overstory trees and 0.6-0.9 μmol m(-2) s(-1) for understory species. The variation in wood CO2 efflux rate was mostly related to wood size, and little to species, canopy layer or height. Mean wood CO2 efflux rate per surface area, derived by regressing CO2 efflux per mass against the ratio of surface

Effect of reaction temperature on structure and fluorescence properties of nitrogen-doped carbon dots

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yi [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Department of Chemistry and Chemical Engineering, Lyuliang University, Lyuliang 033001 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Yaling [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Feng, Xiaoting [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, Feng [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Yang, Yongzhen, E-mail: yyztyut@126.com [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Liu, Xuguang, E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)

2016-11-30

Highlights: • Nitrogen-doped carbon dots (NCDs) from ammonia solution and citric acid were synthesized at different temperatures. • Quantum yield (QY) of NCDs depends largely on the amount of fluorescent polymer chains (FPC), more FPC gives higher QY. • The law of QY of NCDs first increase and then decrease with the reaction temperature increased is found and explained. • Nitrogen doping plays significant role in getting increased UV–vis absorption and QY. - Abstract: To investigate the effect of reaction temperature and nitrogen doping on the structure and fluorescence properties of carbon dots (CDs), six kinds of nitrogen-doped CDs (NCDs) were synthesized at reaction temperatures of 120, 140, 160, 180, 200 and 220 °C, separately, by using citric acid as carbon source and ammonia solution as nitrogen source. Nitrogen-free CDs (N-free CDs-180) was also prepared at 180 °C by using citric acid as the only carbon source for comparison. Results show that reaction temperature has obvious effect on carbonization degree, quantum yield (QY), ultraviolet-visible (UV–vis) absorption and photoluminescence (PL) spectra but less effect on functional groups, nitrogen doping degree and fluorescence lifetime of NCDs. Compared with N-free CDs-180, NCDs-180 possesses enchanced QY and longer fluorescence lifetime. Doping nitrogen has obvious effect on UV–vis absorption and PL spectra but less effect on particles sizes and carbonization degree. The formation mechanism of NCDs is explored: QY of NCDs depends largely on the number of fluorescent polymer chains (FPC), the competition between FPC formation on the surface of NCDs and carbon core growth leads to the change in number of FPC, and consequently to the NCDs with highest QY at appropriate hydrothermal temperature.

Remote sensing of LAI, chlorophyll and leaf nitrogen pools of crop- and grasslands in five European landscapes

KAUST Repository

Boegh, E.; Houborg, Rasmus; Bienkowski, J.; Braban, C.F.; Dalgaard, T.; Van, Dijk, N.; Dragosits, U.; Holmes, E.; Magliulo, V.; Schelde, K.; Di, Tommasi, P.; Vitale, L.; Theobald, M.R.; Cellier, P.; Sutton, M.A.

2013-01-01

Leaf nitrogen and leaf surface area influence the exchange of gases between terrestrial ecosystems and the atmosphere, and play a significant role in the global cycles of carbon, nitrogen and water. The purpose of this study is to use field-based and satellite remote-sensing-based methods to assess leaf nitrogen pools in five diverse European agricultural landscapes located in Denmark, Scotland (United Kingdom), Poland, the Netherlands and Italy. REGFLEC (REGularized canopy reFLECtance) is an advanced image-based inverse canopy radiative transfer modelling system which has shown proficiency for regional mapping of leaf area index (LAI) and leaf chlorophyll (CHLl) using remote sensing data. In this study, high spatial resolution (10-20 m) remote sensing images acquired from the multispectral sensors aboard the SPOT (Satellite For Observation of Earth) satellites were used to assess the capability of REGFLEC for mapping spatial variations in LAI, CHLland the relation to leaf nitrogen (Nl) data in five diverse European agricultural landscapes. REGFLEC is based on physical laws and includes an automatic model parameterization scheme which makes the tool independent of field data for model calibration. In this study, REGFLEC performance was evaluated using LAI measurements and non-destructive measurements (using a SPAD meter) of leaf-scale CHLl and Nl concentrations in 93 fields representing crop- and grasslands of the five landscapes. Furthermore, empirical relationships between field measurements (LAI, CHLl and Nl and five spectral vegetation indices (the Normalized Difference Vegetation Index, the Simple Ratio, the Enhanced Vegetation Index-2, the Green Normalized Difference Vegetation Index, and the green chlorophyll index) were used to assess field data coherence and to serve as a comparison basis for assessing REGFLEC model performance. The field measurements showed strong vertical CHLl gradient profiles in 26% of fields which affected REGFLEC performance as well

Remote sensing of LAI, chlorophyll and leaf nitrogen pools of crop- and grasslands in five European landscapes

KAUST Repository

Boegh, E.

2013-10-07

Leaf nitrogen and leaf surface area influence the exchange of gases between terrestrial ecosystems and the atmosphere, and play a significant role in the global cycles of carbon, nitrogen and water. The purpose of this study is to use field-based and satellite remote-sensing-based methods to assess leaf nitrogen pools in five diverse European agricultural landscapes located in Denmark, Scotland (United Kingdom), Poland, the Netherlands and Italy. REGFLEC (REGularized canopy reFLECtance) is an advanced image-based inverse canopy radiative transfer modelling system which has shown proficiency for regional mapping of leaf area index (LAI) and leaf chlorophyll (CHLl) using remote sensing data. In this study, high spatial resolution (10-20 m) remote sensing images acquired from the multispectral sensors aboard the SPOT (Satellite For Observation of Earth) satellites were used to assess the capability of REGFLEC for mapping spatial variations in LAI, CHLland the relation to leaf nitrogen (Nl) data in five diverse European agricultural landscapes. REGFLEC is based on physical laws and includes an automatic model parameterization scheme which makes the tool independent of field data for model calibration. In this study, REGFLEC performance was evaluated using LAI measurements and non-destructive measurements (using a SPAD meter) of leaf-scale CHLl and Nl concentrations in 93 fields representing crop- and grasslands of the five landscapes. Furthermore, empirical relationships between field measurements (LAI, CHLl and Nl and five spectral vegetation indices (the Normalized Difference Vegetation Index, the Simple Ratio, the Enhanced Vegetation Index-2, the Green Normalized Difference Vegetation Index, and the green chlorophyll index) were used to assess field data coherence and to serve as a comparison basis for assessing REGFLEC model performance. The field measurements showed strong vertical CHLl gradient profiles in 26% of fields which affected REGFLEC performance as well

Worldwide variation in within-canopy photosynthetic acclimation: differences in temporal and environmental controls among plant functional types

Science.gov (United States)

Niinemets, Ülo; Keenan, Trevor

2017-04-01

Major light gradients, characteristically 10- to 50-fold, constitute the most prominent feature of plant canopies. These gradients drive within-canopy variation in foliage structural, chemical and physiological traits. As a key acclimation response to variation in light availability, foliage photosynthetic capacity per area (Aarea) increases with increasing light availability within the canopy, maximizing whole canopy photosynthesis. Recently, a worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types was constructed and within-canopy variation in photosynthetic acclimation was characterized (Niinemets Ü, Keenan TF, Hallik L (2015) Tansley review. A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types. The New Phytologist 205: 973-993). However, the understanding of how within-canopy photosynthetic gradients vary during the growing season and in response to site and stand characteristics is still limited. Here we analyzed temporal, environmental and site (nutrient availability, stand density, ambient CO2 concentration, water availability) sources of variation in within-canopy photosynthetic acclimation in different plant functional types. Variation in key structural (leaf dry mass per unit area, MA), chemical (nitrogen content per dry mass, NM, and area, NA) and physiological (photosynthetic nitrogen use efficiency, EN) photosynthetic capacity per dry mass, Amass and area, Aarea) was examined. The analysis demonstrates major, typically 1.5-2-fold, time-, environment and site-dependent modifications in within-canopy variation in foliage photosynthetic capacity. However, the magnitude and direction of temporal and environmental variations in plasticity significantly varied among functional types. Species with longer leaf life span and low rates of canopy expansion or flush-type canopy

Estimating biophysical properties of coffee (Coffea canephora) plants with above-canopy field measurements, using CropSpec®

Science.gov (United States)

Putra, Bayu T. Widjaja; Soni, Peeyush; Morimoto, Eiji; Pujiyanto, Pujiyanto

2018-04-01

Remote sensing technologies have been applied to many crops, but tree crops like Robusta coffee (Coffea canephora) under shade conditions require additional attention while making above-canopy measurements. The objective of this study was to determine how well chlorophyll and nitrogen status of Robusta coffee plants can be estimated with the laser-based (CropSpec®) active sensor. This study also identified appropriate vegetation indices for estimating Nitrogen content by above-canopy measurement, using near-infra red and red-edge bands. Varying light intensity and different background of the plants were considered in developing the indices. Field experiments were conducted involving different non-destructive tools (CropSpec® and SPAD-502 chlorophyll meter). Subsequently, Kjeldahl laboratory analyses were performed to determine the actual Nitrogen content of the plants with different ages and field conditions used in the non-destructive previous stage. Measurements were undertaken for assessing the biophysical properties of tree plant. The usefulness of near-infrared and red-edge bands from these sensors in measuring critical nitrogen levels of coffee plants by above-canopy measurement are investigated in this study.

Oxygen etching mechanism in carbon-nitrogen (CNx) domelike nanostructures

International Nuclear Information System (INIS)

Acuna, J. J. S.; Figueroa, C. A.; Kleinke, M. U.; Alvarez, F.; Biggemann, D.

2008-01-01

We report a comprehensive study involving the ion beam oxygen etching purification mechanism of domelike carbon nanostructures containing nitrogen. The CN x nanodomes were prepared on Si substrate containing nanometric nickel islands catalyzed by ion beam sputtering of a carbon target and assisting the deposition by a second nitrogen ion gun. After preparation, the samples were irradiated in situ by a low energy ion beam oxygen source and its effects on the nanostructures were studied by x-ray photoelectron spectroscopy in an attached ultrahigh vacuum chamber, i.e., without atmospheric contamination. The influence of the etching process on the morphology of the samples and structures was studied by atomic force microscopy and field emission gun-secondary electron microscopy, respectively. Also, the nanodomes were observed by high resolution transmission electron microscopy. The oxygen atoms preferentially bond to carbon atoms by forming terminal carbonyl groups in the most reactive parts of the nanostructures. After the irradiation, the remaining nanostructures are grouped around two well-defined size distributions. Subsequent annealing eliminates volatile oxygen compounds retained at the surface. The oxygen ions mainly react with nitrogen atoms located in pyridinelike structures

Spectral isotopic methods of determining nitrogen and carbon in plant specimens with laser volatization

International Nuclear Information System (INIS)

Lazeeva, G.S.

1986-01-01

Methods have been devised for the local determination of nitrogen and carbon isotope compositions in plant specimens, which provide separate and joint determination. Local laser evaporation has been combined with spectroscopic determination of the isotope compositions in the gas phase. A continuous-wave CO 2 laser is preferable for the local evaporation; the carbon isotope composition may be determined directly on the sum of the evaporation products, whereas nitrogen must first be separated as N 2 . Methods have also been developed for the local determination of total nitrogen and carbon in a sample with isotope dilution on the basis of laser evaporation. In order to eliminate systematic errors in determining total carbon in plant material, an evaporation method free from a rim has been devised. These methods have been used in determining isotope concentration profiles in plant specimens grown in experiments employing labeled nitrogen and carbon

Stoichiometric carbon nitride synthesized by ion beam sputtering and post nitrogen ion implantation

International Nuclear Information System (INIS)

Valizadeh, R.; Colligon, J.S.; Katardiev, I.V.; Faunce, C.A.; Donnelly, S.E.

1998-01-01

Full text: Carbon nitride films have been deposited on Si (100) by ion beam sputtering a vitreous graphite target with nitrogen and argon ions with and without concurrent N2 ion bombardment at room temperature. The sputtering beam energy was 1000 eV and the assisted beam energy was 300 eV with ion / atom arrival ratio ranging from 0.5 to 5. The carbon nitride films were deposited both as single layer directly on silicon substrate and as multilayer between two layers of stoichiometric amorphous silicon nitride and polycrystalline titanium nitride. The deposited films were implanted ex-situ with 30 keV nitrogen ions with various doses ranging from 1E17 to 4E17 ions.cm -2 and 2 GeV xenon ion with a dose of 1E12 ions.cm -2 . The nitrogen concentration of the films was measured with Rutherford Backscattering (RBS), Secondary Neutral Mass Spectrometry (SNMS) and Parallel Electron Energy Loss Spectroscopy (PEELS). The nitrogen concentration for as deposited sample was 34 at% and stoichiometric carbon nitride C 3 N 4 was achieved by post nitrogen implantation of the multi-layered films. Post bombardment of single layer carbon nitride films lead to reduction in the total nitrogen concentration. Carbon K edge structure obtained from PEELS analysis suggested that the amorphous C 3 N 4 matrix was predominantly sp 2 bonded. This was confirmed by Fourier Transforrn Infra-Red Spectroscopy (FTIR) analysis of the single CN layer which showed the nitrogen was mostly bonded with carbon in nitrile (C≡N) and imine (C=N) groups. The microstructure of the film was determined by Transmission Electron Microscopy (TEM) which indicated that the films were amorphous

Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

Directory of Open Access Journals (Sweden)

Qiliang Wei

2015-09-01

Full Text Available Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs and nitrogen-doped graphene (NG, have attracted increasing attention for oxygen reduction reaction (ORR in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e− transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies.

Distribution and Sources of Carbon, Nitrogen, Phosphorus and ...

Indian Academy of Sciences (India)

69

School of Environmental Sciences, Jawaharlal Nehru University, New Delhi – 110067 ... and macroalgae may be major contributors of organic matter in the lagoon. .... 3.2 Analysis of Carbon, Nitrogen, Phosphorus and Biogenic Silica.

The certification of carbon and nitrogen in molybdenum (BCR No.23)

International Nuclear Information System (INIS)

Vandecasteele, C.

1985-01-01

The experimental procedures used for the certification of carbon and nitrogen in molybdenum (CRM 023), which has already been certified for oxygen, are presented. Samples were analysed by 5 different laboratories using photon and charged particle activation analysis. The analytical methods and the approach used to analyse the data are described. The carbon content is certified to be below 0.2 μg/g; the nitrogen content to be below 0.3 μg/g

Content of nitrogen in waste petroleum carbon for steel industries

International Nuclear Information System (INIS)

Rios, R.O; Jimenez, A.F; Szieber, C.W; Banchik, A.D

2004-01-01

Steel industries use refined carbon as an alloy for steel production. This alloy is produced from waste carbon from the distillation of the petroleum. The refined carbon, called recarburizer, is obtained by calcination at high temperature. Under these thermal conditions the organic molecules decompose and a fraction of the N 2 , S and H 2 , volatile material and moisture are released; while the carbon tends to develop a crystalline structure similar to graphite's. The right combination of calcinations temperature and time in the furnace can optimize the quality of the resulting product. The content of S and N 2 has to be minimized for the use of calcined carbon in the steel industry. Nitrogen content should be reduced by two orders of magnitude, from 1% - 2% down to hundreds of ppm by weight. This work describes the activities undertaken to obtain calcined coke from petroleum from crude oil carbon that satisfies the requirements of the Mercosur standard 02:00-169 (Pending) for use as a carborizer in steels industries. To satisfy the requirements of the Mercosur standards NM 236:00 IRAM-IAS-NM so that graphite is used as a carburizer a content of 300 ppm maximum weight of nitrogen has to be obtained. So the first stage in this development is to define a production process for supplying calcined coke in the range of nitrogen concentrations required by the Mercosur standards (CW)

Organic carbon, nitrogen and phosphorus contents of some tea soils

International Nuclear Information System (INIS)

Ahmed, M.S.; Zamir, M.R.; Sanauallah, A.F.M.

2005-01-01

Soil samples were collected from Rungicherra Tea-Estate of Moulvibazar district, Bangladesh. Organic carbon, organic matter, total nitrogen and available phosphorus content of the collected soil of different topographic positions have been determined. The experimental data have been analyzed statistically and plotted against topography and soil depth. Organic carbon and organic matter content varied from 0.79 to 1.24% and 1.37 to 2.14%. respectively. Total nitrogen and available phosphorus content of these soils varied respectively from 0.095 to 0.13% and 2.31 to 4.02 ppm. (author)

[Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].

Science.gov (United States)

Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng

2010-11-01

The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in stabilization index (SI(C) and SI(N)) of the organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen.

Nitrogen-enriched bituminous coal-based active carbons as materials for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

R. Pietrzak; K. Jurewicz; P. Nowicki; K. Babel; H. Wachowska [A. Mickiewicz University, Poznan (Poland). Laboratory of Coal Chemistry and Technology

2010-11-15

The paper presents the results of a study on obtaining N-enriched active carbons from bituminous coal and on testing its use as an electrode material in supercapacitors. The coal was carbonised, activated with KOH and ammoxidised by a mixture of ammonia and air at the ratio 1:3 at 300{sup o}C or 350{sup o}C, at different stages of the production, that is, at those of precursor, carbonisate, and active carbon. The products were microporous N-enriched active carbon samples of well-developed surface area reaching from 1577 to 2510 m{sup 2}/g and containing 1.0 to 8.5 wt% of nitrogen. The XPS measurements have shown that in the active carbons enriched in nitrogen at the stage of precursor and at the stage of carbonisate, the dominant nitrogen species are the N-5 groups, while in the samples ammoxidised at the last stage of the treatment the dominant nitrogen species are the surface groups of imines and/or nitriles, probably accompanied by amines and amides. The paper reports the results of a comprehensive study of the effect of the structure and chemical composition of a series of active carbon samples of different properties on their capacity performance in water solutions of H{sub 2}SO{sub 4} or KOH, with the behaviour of positive and negative electrodes analysed separately. 33 refs., 7 figs., 8 tabs.

Synthesis of Nitrogen-Doped Mesoporous Carbon for the Catalytic Oxidation of Ethylbenzene

Science.gov (United States)

Wang, Ruicong; Yu, Yifeng; Zhang, Yue; Lv, Haijun; Chen, Aibing

2017-06-01

Nitrogen-doped ordered mesoporous carbon (NOMC) was fabricated via a simple hard-template method by functionalized ionic liquids as carbon and nitrogen source, SBA-15 as a hard-template. The obtained NOMC materials have a high nitrogen content of 5.55 %, a high surface area of 446.2 m2 g-1, and an excellent performance in catalysing oxidation of ethylbenzene. The conversion rate of ethylbenzene can be up to 84.5% and the yield of acetophenone can be up to 69.9%, the results indicated that the NOMC materials have a faster catalytic rate and a higher production of acetophenone than catalyst-free and CMK-3, due to their uniform pore size, high surface area and rich active sites in the carbon pore walls.

Role of nitrogen in pore development in activated carbon prepared by potassium carbonate activation of lignin

Energy Technology Data Exchange (ETDEWEB)

Tsubouchi, Naoto, E-mail: tsubon@eng.hokudai.ac.jp; Nishio, Megumi; Mochizuki, Yuuki

2016-05-15

Highlights: • Activated carbon prepared from a lignin/urea/K{sub 2}CO{sub 3} mixture provides a high specific surface area and a large pore volume. • Part of the urea nitrogen present in the mixture is retained as heterocyclic nitrogen in the solid phase after activation/carbonization. • Pore development is thought to proceed through interactions between K-species and C–N forms. - Abstract: The present work focuses on the role of nitrogen in the development of pores in activated carbon produced from lignin by K{sub 2}CO{sub 3} activation, employing a fixed bed reactor under a high-purity He stream at temperatures of 500–900 °C. The specific surface area and pore volume obtained by activation of lignin alone are 230 m{sup 2}/g and 0.13 cm{sup 3}/g at 800 °C, and 540 m{sup 2}/g and 0.31 cm{sup 3}/g at 900 °C, respectively. Activation of a mixture of lignin and urea provides a significant increase in the surface area and volume, respectively reaching 3300–3400 m{sup 2}/g and 2.0–2.3 cm{sup 3}/g after holding at 800–900 °C for 1 h. Heating a lignin/urea/K{sub 2}CO{sub 3} mixture leads to a significant decrease in the yield of released N-containing gases compared to the results for urea alone and a lignin/urea mixture, and most of the nitrogen in the urea is retained in the solid phase. X-ray photoelectron spectroscopy and X-ray diffraction analyses clearly show that part of the remaining nitrogen is present in heterocyclic structures (for example, pyridinic and pyrrolic nitrogen), and the rest is contained as KOCN at ≤600 °C and as KCN at ≥700 °C, such that the latter two compounds can be almost completely removed by water washing. The fate of nitrogen during heating of lignin/urea/K{sub 2}CO{sub 3} and role of nitrogen in pore development in activated carbon are discussed on the basis of the results mentioned above.

Distinguishing ectomycorrhizal and saprophytic fungi using carbon and nitrogen isotopic compositions

Directory of Open Access Journals (Sweden)

Weiguo Hou

2012-05-01

Full Text Available Ectomycorrhizal fungi, a group of widespread symbiotic fungi with plant, obtain carbon source from trees and improve plant mineral nutrient uptake with their widespread hyphal network. Ectomycorrhizal fungi can be used as inoculants to improve the survival rates of plantation. Saprophytic fungi use the nutrition from the debris of plant or animals, and it is difficult to distinguish the saprophytic and ectomycorrhizal fungi by morphological and anatomic methods. In this research, the differences of stable carbon and nitrogen isotopic compositions of these fungi were analyzed. The results showed that the abundances of 13C of were higher than those of ectomycorrhizal fungi and the abundances of 15N of saprophytic fungi were lower than those of ectomycorrhizal fungi. Such differences of stable carbon and nitrogen isotopic compositions between ectomycorrhizal fungi and saprophytic fungi can be ascribed to their different nutrition sources and ecological functions. These results collectively indicate that stable carbon and nitrogen isotopic compositions are an effective proxy for distinguishing between ectomycorrhizal and saprophytic fungi.

A co-confined carbonization approach to aligned nitrogen-doped mesoporous carbon nanofibers and its application as an adsorbent

International Nuclear Information System (INIS)

Chen, Aibing; Liu, Chao; Yu, Yifeng; Hu, Yongqi; Lv, Haijun; Zhang, Yue; Shen, Shufeng; Zhang, Jian

2014-01-01

Highlights: • MCNFs were synthesized by a co-confined carbonization method. • The diameter size of MCNFs with bimodal mesoporous structure can be modulated. • The obtained MCNFs manifest better adsorption capacity for SO 2 , CO 2 and Cd 2+ . - Abstract: Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethylorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal mesoporous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO 2 and CO 2 . Cyclic experiments revealed a considerable stability of MCNFs over 20 runs of SO 2 adsorption and 15 runs for CO 2 adsorption. The MCNFs also have a preferable adsorption performance for Cd 2+

Canopy Version 7.0: Canopy manual

International Nuclear Information System (INIS)

Fischler, M.; Uchima, M.; Hockney, G.; Mackenzie, P.

1993-12-01

Canopy provides a machine-independent environment for attacking grid-oriented problems. This document describes the concepts and routines common to all Canopy implementations, independent of the system and implementation. Information specific to the massively parallel ACPMAPS/indexACPMAPS system at FermiLab is contained in two other documents: The CANOPY ACPMAPS USER's GUIDE provides user-oriented instructions on compiling, running, file system usage, and production job control. The CANOPY ACPMAPS SYSTEM MANUAL describes system tools and installation and system management techniques. System-specific User's Guides may be created for implementations on other systems. The goal of Canopy is to allow scientists to use massively parallel systems for a broad class of applications without having to become expert in any particular system or in parallel programming techniques. The Canopy approach identifies grid-oriented concepts and implements them as routines in a library. Applications written in terms of these concepts will run on any system which supports the Canopy software. A side benefit in dealing with familiar concepts is that programs can more easily be understood by other researchers

Impacts of Human Induced Nitrogen Deposition on Ecosystem Carbon Sequestration and Water Balance in China

Science.gov (United States)

Sheng, M.; Yang, D.; Tang, J.; Lei, H.

2017-12-01

Enhanced plant biomass accumulation in response to elevated atmospheric CO2 concentration could dampen the future rate of increase in CO2 levels and associated climate warming. However, many experiments around the world reported that nitrogen availability could limit the sustainability of the ecosystems' response to elevated CO2. In the recent 20 years, atmospheric nitrogen deposition, primarily from fossil fuel combustion, has increased sharply about 25% in China and meanwhile, China has the highest carbon emission in the world, implying a large opportunity to increase vegetation greenness and ecosystem carbon sequestration. Moreover, the water balance of the ecosystem will also change. However, in the future, the trajectory of increasing nitrogen deposition from fossil fuel use is to be controlled by the government policy that shapes the energy and industrial structure. Therefore, the historical and future trajectories of nitrogen deposition are likely very different, and it is imperative to understand how changes in nitrogen deposition will impact the ecosystem carbon sequestration and water balance in China. We here use the Community Land Model (CLM 4.5) to analyze how the change of nitrogen deposition has influenced and will influence the ecosystem carbon and water cycle in China at a high spatial resolution (0.1 degree). We address the following questions: 1) what is the contribution of the nitrogen deposition on historical vegetation greenness? 2) How does the change of nitrogen deposition affect the carbon sequestration? 3) What is its influence to water balance? And 4) how different will be the influence of the nitrogen deposition on ecosystem carbon and water cycling in the future?

Estimation of winter wheat canopy nitrogen density at different growth stages based on Multi-LUT approach

Science.gov (United States)

Li, Zhenhai; Li, Na; Li, Zhenhong; Wang, Jianwen; Liu, Chang

2017-10-01

Rapid real-time monitoring of wheat nitrogen (N) status is crucial for precision N management during wheat growth. In this study, Multi Lookup Table (Multi-LUT) approach based on the N-PROSAIL model parameters setting at different growth stages was constructed to estimating canopy N density (CND) in winter wheat. The results showed that the estimated CND was in line with with measured CND, with the determination coefficient (R2) and the corresponding root mean square error (RMSE) values of 0.80 and 1.16 g m-2, respectively. Time-consuming of one sample estimation was only 6 ms under the test machine with CPU configuration of Intel(R) Core(TM) i5-2430 @2.40GHz quad-core. These results confirmed the potential of using Multi-LUT approach for CND retrieval in winter wheat at different growth stages and under variables climatic conditions.

Nitrogen deposition, land cover conversion, climate, and contemporary carbon balance of Europe (Invited)

Science.gov (United States)

Churkina, G.; Zahle, S.; Hughes, J.; Viovy, N.; Chen, Y.; Jung, M.; Ramankutty, N.; Roedenbeck, C.; Heimann, M.; Jones, C.

2009-12-01

In Europe, atmospheric nitrogen deposition has more than doubled, air temperature was rising, forest cover was steadily increasing, while agricultural area was declining over the last 50 years. What effect have these changes had on the European carbon balance? In this study we estimate responses of the European land ecosystems to nitrogen deposition, rising CO2, land cover conversion and climate change. We use results from three ecosystem process models such as BIOME-BGC, JULES, and ORCHIDEE (-CN) to address this question. We discuss to which degree carbon balance of Europe has been altered by nitrogen deposition in comparison to other drivers and identify areas which carbon balance has been affected by anthropogenic changes the most. We also analyze ecosystems carbon pools which were affected by the abovementioned environmental changes.

The influence of different nitrogen and carbon sources on mycotoxin production in Alternaria alternata.

Science.gov (United States)

Brzonkalik, Katrin; Herrling, Tanja; Syldatk, Christoph; Neumann, Anke

2011-05-27

The aim of this study was to determine the influence of different carbon and nitrogen sources on the production of the mycotoxins alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) by Alternaria alternata at 28°C using a semi-synthetic medium (modified Czapek-Dox broth) supplemented with nitrogen and carbon sources. Additionally the effect of shaken and static cultivation on mycotoxin production was tested. Initial experiments showed a clear dependency between nitrogen depletion and mycotoxin production. To assess whether nitrogen limitation in general or the type of nitrogen source triggers the production, various nitrogen sources including several ammonium/nitrate salts and amino acids were tested. In static culture the production of AOH/AME can be enhanced greatly with phenylalanine whereas some nitrogen sources seem to inhibit the AOH/AME production completely. TA was not significantly affected by the choice of nitrogen source. In shaken culture the overall production of all mycotoxins was lower compared to static cultivation. Furthermore tests with a wide variety of carbon sources including monosaccharides, disaccharides, complex saccharides such as starch as well as glycerol and acetate were performed. In shaken culture AOH was produced when glucose, fructose, sucrose, acetate or mixtures of glucose/sucrose and glucose/acetate were used as carbon sources. AME production was not detected. The use of sodium acetate resulted in the highest AOH production. In static culture AOH production was also stimulated by acetate and the amount is comparable to shaken conditions. Under static conditions production of AOH was lower except when cultivated with acetate. In static cultivation 9 of 14 tested carbon sources induced mycotoxin production compared to 4 in shaken culture. This is the first study which analyses the influence of carbon and nitrogen sources in a semi-synthetic medium and assesses the effects of culture conditions on

Explaining biomass growth of tropical canopy trees: the importance of sapwood.

Science.gov (United States)

van der Sande, Masha T; Zuidema, Pieter A; Sterck, Frank

2015-04-01

Tropical forests are important in worldwide carbon (C) storage and sequestration. C sequestration of these forests may especially be determined by the growth of canopy trees. However, the factors driving variation in growth among such large individuals remain largely unclear. We evaluate how crown traits [total leaf area, specific leaf area and leaf nitrogen (N) concentration] and stem traits [sapwood area (SA) and sapwood N concentration] measured for individual trees affect absolute biomass growth for 43 tropical canopy trees belonging to four species, in a moist forest in Bolivia. Biomass growth varied strongly among trees, between 17.3 and 367.3 kg year(-1), with an average of 105.4 kg year(-1). We found that variation in biomass growth was chiefly explained by a positive effect of SA, and not by tree size or other traits examined. SA itself was positively associated with sapwood growth, sapwood lifespan and basal area. We speculate that SA positively affects the growth of individual trees mainly by increasing water storage, thus securing water supply to the crown. These positive roles of sapwood on growth apparently offset the increased respiration costs incurred by more sapwood. This is one of the first individual-based studies to show that variation in sapwood traits-and not crown traits-explains variation in growth among tropical canopy trees. Accurate predictions of C dynamics in tropical forests require similar studies on biomass growth of individual trees as well as studies evaluating the dual effect of sapwood (water provision vs. respiratory costs) on tropical tree growth.

A high-performance mesoporous carbon supported nitrogen-doped carbon electrocatalyst for oxygen reduction reaction

Science.gov (United States)

Xu, Jingjing; Lu, Shiyao; Chen, Xu; Wang, Jianan; Zhang, Bo; Zhang, Xinyu; Xiao, Chunhui; Ding, Shujiang

2017-12-01

Investigating low-cost and highly active electrocatalysts for oxygen reduction reactions (ORR) is of crucial importance for energy conversion and storage devices. Herein, we design and prepare mesoporous carbon supported nitrogen-doped carbon by pyrolysis of polyaniline coated on CMK-3. This electrocatalyst exhibits excellent performance towards ORR in alkaline media. The optimized nitrogen-doped mesoporous electrocatalyst show an onset potential (E onset) of 0.95 V (versus reversible hydrogen electrode (RHE)) and half-wave potential (E 1/2) of 0.83 V (versus RHE) in 0.1 M KOH. Furthermore, the as-prepared catalyst presents superior durability and methanol tolerance compared to commercial Pt/C indicating its potential applications in fuel cells and metal-air batteries.

Biodiversity Meets the Atmosphere: A Global View of Forest Canopies

Science.gov (United States)

C. M. P. Ozanne; D. Anhuf; S. L. Boulter; M. Keller; R. L. Kitching; C. Korner; F. C. Meinzer; A. W. Mitchell; T. Nakashizuka; P. L. Silva Dias; N. E. Stork; S. J. Wright; M Yoshimura

2003-01-01

The forest canopy is the functional interface between 90% of Earth’s terrestrial biomass and the atmosphere. Multidisciplinary research in the canopy has expanded concepts of global species richness, physiological processes, and the provision of ecosystem services. Trees respond in a species-specific manner to elevated carbon dioxide levels, while climate change...

Facile preparation of nitrogen-doped hierarchical porous carbon with high performance in supercapacitors

International Nuclear Information System (INIS)

Yan, Kun; Kong, Ling-Bin; Shen, Kui-Wen; Dai, Yan-Hua; Shi, Ming; Hu, Bing; Luo, Yong-Chun; Kang, Long

2016-01-01

Graphical abstract: Preparing and activating process of nitrogen-doped hierarchical porous carbon (NHPC). - Highlights: • The well-defined PAN-b-PMMA copolymer was synthesized by atom transfer radical polymerization with narrow molecular weight distribution. • Nitrogen-doped hierarchical porous structure (NHPC) was prepared through a simple carbonization procedure of PAN-b-PMMA precursor. • NHPC possessed hierarchical porous structure with high BET surface area of 257 m"2 g"−"1 and DFT mesopore size of 14.61 nm. • Effects of activation conditions on supercapacitive behavior were systematically studied. - Abstract: The nitrogen-doped hierarchical porous carbon (NHPC) material was successfully prepared through a simple carbonization procedure of well-defined diblock copolymer precursor containing nitrogen-enriched carbon source, i.e., polyacrylonitrile (PAN), and asacrificial block, i.e., polymethylmethacrylate (PMMA). PAN-b-PMMA diblock copolymer was synthesized by atom transfer radical polymeriation (ATRP) with narrow molecular weight distribution. The as-obtained NHPC possessed nitrogen-doped hierarchical porous structure with high BET surface area of 257 m"2 g"−"1 and Nonlocal density functional theory (NLDFT) mesopore size of 14.61 nm. Surface activated nitrogen-doped hierarchical porous carbon (A-NHPC) materials were obtained by subsequent surface activation with HNO_3 solution. The effects of activation conditions on supercapacitive behavior were systematically studied, a maximum specific capacitance of 314 F g"−"1 at a current density of 0.5 A g"−"1 was achieved in 2 M KOH aqueous electrolyte. Simultaneously, it exhibited excellent rate capability of 67.8% capacitance retention as the current density increased from 0.5 to 20 A g"−"1 and superior cycling performance of 90% capacitance retention after 10,000 cycles at the current density of 2 A g"−"1.

Facile preparation of nitrogen-doped hierarchical porous carbon with high performance in supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Yan, Kun [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Kong, Ling-Bin, E-mail: konglb@lut.cn [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Shen, Kui-Wen; Dai, Yan-Hua; Shi, Ming; Hu, Bing [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Luo, Yong-Chun; Kang, Long [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China)

2016-02-28

Graphical abstract: Preparing and activating process of nitrogen-doped hierarchical porous carbon (NHPC). - Highlights: • The well-defined PAN-b-PMMA copolymer was synthesized by atom transfer radical polymerization with narrow molecular weight distribution. • Nitrogen-doped hierarchical porous structure (NHPC) was prepared through a simple carbonization procedure of PAN-b-PMMA precursor. • NHPC possessed hierarchical porous structure with high BET surface area of 257 m{sup 2} g{sup −1} and DFT mesopore size of 14.61 nm. • Effects of activation conditions on supercapacitive behavior were systematically studied. - Abstract: The nitrogen-doped hierarchical porous carbon (NHPC) material was successfully prepared through a simple carbonization procedure of well-defined diblock copolymer precursor containing nitrogen-enriched carbon source, i.e., polyacrylonitrile (PAN), and asacrificial block, i.e., polymethylmethacrylate (PMMA). PAN-b-PMMA diblock copolymer was synthesized by atom transfer radical polymeriation (ATRP) with narrow molecular weight distribution. The as-obtained NHPC possessed nitrogen-doped hierarchical porous structure with high BET surface area of 257 m{sup 2} g{sup −1} and Nonlocal density functional theory (NLDFT) mesopore size of 14.61 nm. Surface activated nitrogen-doped hierarchical porous carbon (A-NHPC) materials were obtained by subsequent surface activation with HNO{sub 3} solution. The effects of activation conditions on supercapacitive behavior were systematically studied, a maximum specific capacitance of 314 F g{sup −1} at a current density of 0.5 A g{sup −1} was achieved in 2 M KOH aqueous electrolyte. Simultaneously, it exhibited excellent rate capability of 67.8% capacitance retention as the current density increased from 0.5 to 20 A g{sup −1} and superior cycling performance of 90% capacitance retention after 10,000 cycles at the current density of 2 A g{sup −1}.

Synthesis of Nitrogen-doped Carbon Nanotubes with Layered ...

African Journals Online (AJOL)

NICO

Nitrogen-doped carbon nanotubes (CNx) were synthesized by the catalytic chemical vapour deposition ... dispersed metal nanoparticles over oxide matrices can be obtained ..... 18 S.Y. Kim, J. Lee, C.W. Na, J. Park, K. Seo and B. Kim, Chem.

Improved Electrochemical Performance of Biomass-Derived Nanoporous Carbon/Sulfur Composites Cathode for Lithium-Sulfur Batteries by Nitrogen Doping

International Nuclear Information System (INIS)

Geng, Zhen; Xiao, Qiangfeng; Wang, Dabin; Yi, Guanghai; Xu, Zhigang; Li, Bing; Zhang, Cunman

2016-01-01

A two-step method with high-efficiency is developed to prepare nitrogen doped activated carbons (NACs) with high surface area and nitrogen content. Based on the method, series of NACs with similar surface area and pore texture but different nitrogen content and nitrogen group species are successfully prepared. The influence of nitrogen doping on electrochemical performance of carbon/sulfur composites cathode is studied deeply under the conditions of similar surface area and pore texture. It presents the directly experimental demonstration that both nitrogen content and nitrogen group species play crucial roles on electrochemical performance of carbon/sulfur composites cathode. NAC/sulfur composites show the much improved cycling performance, which is about 3.5 times as that of nitrogen free carbon. Improved electrochemical performance is due to synergistic effects between nitrogen content and effective nitrogen groups, which enables effective trapping of lithium polysulfides within carbon framework. Besides, it is found that oxygen groups exist in carbon materials obviously influence electrochemical performance of cathode, which could be ignored in most of studies. Based on above, it can be concluded that enhanced chemisorption to lithium polysulfides by functional groups modification is the effective route to improve the electrochemical performance of Li-S battery.

Exchange of reactive nitrogen compounds: concentrations and fluxes of total ammonium and total nitrate above a spruce canopy

Directory of Open Access Journals (Sweden)

V. Wolff

2010-05-01

Full Text Available Total ammonium (tot-NH₄⁺ and total nitrate (tot-NO₃⁻ provide chemically conservative quantities in the measurement of surface exchange of reactive nitrogen compounds ammonia (NH₃, particulate ammonium (NH₄⁺, nitric acid (HNO₃, and particulate nitrate (NO₃⁻, using the aerodynamic gradient method. Total fluxes were derived from concentration differences of total ammonium (NH₃ and NH₄⁺ and total nitrate (HNO₃ and NO₃⁻ measured at two levels. Gaseous species and related particulate compounds were measured selectively, simultaneously and continuously above a spruce forest canopy in south-eastern Germany in summer 2007. Measurements were performed using a wet-chemical two-point gradient instrument, the GRAEGOR. Median concentrations of NH₃, HNO₃, NH₄⁺, and NO₃⁻ were 0.57, 0.12, 0.76, and 0.48 μg m⁻³, respectively. Total ammonium and total nitrate fluxes showed large variations depending on meteorological conditions, with concentrations close to zero under humid and cool conditions and higher concentrations under dry conditions. Mean fluxes of total ammonium and total nitrate in September 2007 were directed towards the forest canopy and were −65.77 ng m⁻² s⁻¹ and −41.02 ng m⁻² s⁻¹ (in terms of nitrogen, respectively. Their deposition was controlled by aerodynamic resistances only, with very little influence of surface resistances. Including measurements of wet deposition and findings of former studies on occult deposition (fog water interception at the study site, the total N deposition in September 2007 was estimated to 5.86 kg ha⁻¹.

Improving canopy sensor algorithms with soil and weather information

Science.gov (United States)

Nitrogen (N) need to support corn (Zea mays L.) production can be highly variable within fields. Canopy reflectance sensing for assessing crop N health has been implemented on many farmers’ fields to side-dress or top-dress variable-rate N application, but at times farmers report the performance of ...

Carbon amendment stimulates benthic nitrogen cycling during the bioremediation of particulate aquaculture waste

Science.gov (United States)

Robinson, Georgina; MacTavish, Thomas; Savage, Candida; Caldwell, Gary S.; Jones, Clifford L. W.; Probyn, Trevor; Eyre, Bradley D.; Stead, Selina M.

2018-03-01

The treatment of organic wastes remains one of the key sustainability challenges facing the growing global aquaculture industry. Bioremediation systems based on coupled bioturbation-microbial processing offer a promising route for waste management. We present, for the first time, a combined biogeochemical-molecular analysis of the short-term performance of one such system that is designed to receive nitrogen-rich particulate aquaculture wastes. Using sea cucumbers (Holothuria scabra) as a model bioturbator we provide evidence that adjusting the waste C : N from 5 : 1 to 20 : 1 promoted a shift in nitrogen cycling pathways towards the dissimilatory nitrate reduction to ammonium (DNRA), resulting in net NH4+ efflux from the sediment. The carbon amended treatment exhibited an overall net N2 uptake, whereas the control receiving only aquaculture waste exhibited net N2 production, suggesting that carbon supplementation enhanced nitrogen fixation. The higher NH4+ efflux and N2 uptake was further supported by meta-genome predictions that indicate that organic-carbon addition stimulated DNRA over denitrification. These findings indicate that carbon addition may potentially result in greater retention of nitrogen within the system; however, longer-term trials are necessary to determine whether this nitrogen retention is translated into improved sea cucumber biomass yields. Whether this truly constitutes a remediation process is open for debate as there remains the risk that any increased nitrogen retention may be temporary, with any subsequent release potentially raising the eutrophication risk. Longer and larger-scale trials are required before this approach may be validated with the complexities of the in-system nitrogen cycle being fully understood.

Predicting tropical plant physiology from leaf and canopy spectroscopy.

Science.gov (United States)

Doughty, Christopher E; Asner, Gregory P; Martin, Roberta E

2011-02-01

A broad regional understanding of tropical forest leaf photosynthesis has long been a goal for tropical forest ecologists, but it has remained elusive due to difficult canopy access and high species diversity. Here we develop an empirical model to predict sunlit, light-saturated, tropical leaf photosynthesis using leaf and simulated canopy spectra. To develop this model, we used partial least squares (PLS) analysis on three tropical forest datasets (159 species), two in Hawaii and one at the biosphere 2 laboratory (B2L). For each species, we measured light-saturated photosynthesis (A), light and CO(2) saturated photosynthesis (A(max)), respiration (R), leaf transmittance and reflectance spectra (400-2,500 nm), leaf nitrogen, chlorophyll a and b, carotenoids, and leaf mass per area (LMA). The model best predicted A [r(2) = 0.74, root mean square error (RMSE) = 2.9 μmol m(-2) s(-1))] followed by R (r(2) = 0.48), and A(max) (r(2) = 0.47). We combined leaf reflectance and transmittance with a canopy radiative transfer model to simulate top-of-canopy reflectance and found that canopy spectra are a better predictor of A (RMSE = 2.5 ± 0.07 μmol m(-2) s(-1)) than are leaf spectra. The results indicate the potential for this technique to be used with high-fidelity imaging spectrometers to remotely sense tropical forest canopy photosynthesis.

Extraction of Uranium Using Nitrogen Dioxide and Carbon Dioxide for Spent Fuel Reprocessing

Energy Technology Data Exchange (ETDEWEB)

Kayo Sawada; Daisuke Hirabayashi; Youichi Enokida [EcoTopia Science Institute, Nagoya University, Nagoya, 464-8603 (Japan)

2008-07-01

For the reprocessing of spent nuclear fuels, a new method to extract actinides from spent fuel using highly compressed gases, nitrogen dioxide and carbon dioxide was proposed. Uranium extraction from broken pieces, whose average grain size was 5 mm, of uranium dioxide pellet with nitrogen dioxide and carbon dioxide was demonstrated in the present study. (authors)

Phosphorus and nitrogen-containing carbons obtained by the carbonization of conducting polyaniline complex with phosphites

Czech Academy of Sciences Publication Activity Database

Bober, Patrycja; Trchová, Miroslava; Morávková, Zuzana; Kovářová, Jana; Vulić, I.; Gavrilov, N.; Pašti, I. A.; Stejskal, Jaroslav

2017-01-01

Roč. 246, 20 August (2017), s. 443-450 ISSN 0013-4686 R&D Projects: GA ČR(CZ) GA16-02787S Institutional support: RVO:61389013 Keywords : carbonization * conducting polymer * nitrogen-containing carbon Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 4.798, year: 2016

Carbon Concentration and Carbon-to-Nitrogen Ratio Influence Submerged-Culture Conidiation by the Potential Bioherbicide Colletotrichum truncatum NRRL 13737

Science.gov (United States)

Jackson, Mark A.; Bothast, Rodney J.

1990-01-01

We assessed the influence of various carbon concentrations and carbon-to-nitrogen (C:N) ratios on Colletotrichum truncatum NRRL 13737 conidium formation in submerged cultures grown in a basal salts medium containing various amounts of glucose and Casamino Acids. Under the nutritional conditions tested, the highest conidium concentrations were produced in media with carbon concentrations of 4.0 to 15.3 g/liter. High carbon concentrations (20.4 to 40.8 g/liter) inhibited sporulation and enhanced the formation of microsclerotiumlike hyphal masses. At all the carbon concentrations tested, a culture grown in a medium with a C:N ratio of 15:1 produced more conidia than cultures grown in media with C:N ratios of 40:1 or 5:1. While glucose exhaustion was often coincident with conidium formation, cultures containing residual glucose sporulated and those with high carbon concentrations (>25 g/liter) exhausted glucose without sporulation. Nitrogen source studies showed that the levels of C. truncatum NRRL 13737 conidiation were similar for all protein hydrolysates tested. Reduced conidiation occurred when amino acid and inorganic nitrogen sources were used. Of the nine carbon sources evaluated, acetate as the sole carbon source resulted in the lowest level of sporulation. Images PMID:16348348

Canopy structural alterations to nitrogen functions of the soil microbial community in a Quercus virginiana forest

Science.gov (United States)

Moore, L. D.; Van Stan, J. T., II; Rosier, C. L.; Gay, T. E.; Wu, T.

2014-12-01

Forest canopy structure controls the timing, amount and chemical character of precipitation supply to soils through interception and drainage along crown surfaces. Yet, few studies have examined forest canopy structural connections to soil microbial communities (SMCs), and none have measured how this affects SMC N functions. The maritime Quercus virginiana Mill. (southern live oak) forests of St Catherine's Island, GA, USA provide an ideal opportunity to examine canopy structural alterations to SMCs and their functioning, as their throughfall varies substantially across space due to dense Tillandsia usneoides L. (spanish moss) mats bestrewn throughout. To examine the impact of throughfall variability on SMC N functions, we examined points along the canopy coverage continuum: large canopy gaps (0%), bare canopy (50-60%), and canopy of heavy T. usneoides coverage (>=85%). Five sites beneath each of the canopy cover types were monitored for throughfall water/ions and soil leachates chemistry for one storm each month over the growing period (7 months, Mar-2014 to Sep-2014) to compare with soil chemistry and SMC communities sampled every two months throughout that same period (Mar, May, Jul, Sep). DGGE and QPCR analysis of the N functioning genes (NFGs) to characterize the ammonia oxidizing bacterial (AOB-amoA), archaea (AOA-amoA), and ammonification (chiA) communities were used to determine the nitrification and decomposition potential of these microbial communities. PRS™-probes (Western Ag Innovations Inc., Saskatoon, Canada) were then used to determine the availability of NO3-N and NH4+N in the soils over a 6-week period to evaluate whether the differing NFG abundance and community structures resulted in altered N cycling.

A co-confined carbonization approach to aligned nitrogen-doped mesoporous carbon nanofibers and its application as an adsorbent

Energy Technology Data Exchange (ETDEWEB)

Chen, Aibing [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Liu, Chao [College of Gemmology and Material Technics, Shijiazhuang University of Economic, Huaian Road 136, Shijiazhuang 050031 (China); Yu, Yifeng; Hu, Yongqi; Lv, Haijun; Zhang, Yue; Shen, Shufeng [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Zhang, Jian [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2014-07-15

Highlights: • MCNFs were synthesized by a co-confined carbonization method. • The diameter size of MCNFs with bimodal mesoporous structure can be modulated. • The obtained MCNFs manifest better adsorption capacity for SO{sub 2}, CO{sub 2} and Cd{sup 2+}. - Abstract: Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethylorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal mesoporous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO{sub 2} and CO{sub 2}. Cyclic experiments revealed a considerable stability of MCNFs over 20 runs of SO{sub 2} adsorption and 15 runs for CO{sub 2} adsorption. The MCNFs also have a preferable adsorption performance for Cd{sup 2+}.

Canopy position affects the relationships between leaf respiration and associated traits in a tropical rainforest in Far North Queensland.

Science.gov (United States)

Weerasinghe, Lasantha K; Creek, Danielle; Crous, Kristine Y; Xiang, Shuang; Liddell, Michael J; Turnbull, Matthew H; Atkin, Owen K

2014-06-01

We explored the impact of canopy position on leaf respiration (R) and associated traits in tree and shrub species growing in a lowland tropical rainforest in Far North Queensland, Australia. The range of traits quantified included: leaf R in darkness (RD) and in the light (RL; estimated using the Kok method); the temperature (T)-sensitivity of RD; light-saturated photosynthesis (Asat); leaf dry mass per unit area (LMA); and concentrations of leaf nitrogen (N), phosphorus (P), soluble sugars and starch. We found that LMA, and area-based N, P, sugars and starch concentrations were all higher in sun-exposed/upper canopy leaves, compared with their shaded/lower canopy and deep-shade/understory counterparts; similarly, area-based rates of RD, RL and Asat (at 28 °C) were all higher in the upper canopy leaves, indicating higher metabolic capacity in the upper canopy. The extent to which light inhibited R did not differ significantly between upper and lower canopy leaves, with the overall average inhibition being 32% across both canopy levels. Log-log RD-Asat relationships differed between upper and lower canopy leaves, with upper canopy leaves exhibiting higher rates of RD for a given Asat (both on an area and mass basis), as well as higher mass-based rates of RD for a given [N] and [P]. Over the 25-45 °C range, the T-sensitivity of RD was similar in upper and lower canopy leaves, with both canopy positions exhibiting Q10 values near 2.0 (i.e., doubling for every 10 °C rise in T) and Tmax values near 60 °C (i.e., T where RD reached maximal values). Thus, while rates of RD at 28 °C decreased with increasing depth in the canopy, the T-dependence of RD remained constant; these findings have important implications for vegetation-climate models that seek to predict carbon fluxes between tropical lowland rainforests and the atmosphere. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Making C4 crops more water efficient under current and future climate: Tradeoffs between carbon gain and water loss

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Srinivasan, V.; Pignon, C.

2017-12-01

C4 plants have a carbon concentrating mechanism that has evolved under historically low CO2 concentrations of around 200 ppm. However, increases in global CO2 concentrations in recent times (current CO2 concentrations are at 400 ppm and it is projected to be 550 ppm by mid-century) have diminished the relative advantage of C4 plants over C3 plants, which lack the expensive carbon concentrating machinery. Here we show by employing model simulations that under pre-historic CO2 concentrations, C4 plants are near optimal in their stomatal behavior and nitrogen partitioning between carbon concentrating machinery and carboxylation machinery, and they are significantly supra-optimal under current and future elevated CO2 concentrations. Model simulations performed at current CO2 concentrations of 400 ppm show that, under high light conditions, decreasing stomatal conductance by 20% results in a 15% increase in water use efficiency with negligible loss in photosynthesis. Under future elevated CO2 concentrations of 550 ppm, a 40% decrease in stomatal conductance produces a 35% increase in water use efficiency. Furthermore, stomatal closure is shown to be more effective in decreasing whole canopy transpiration compared to canopy top leaf transpiration, since shaded leaves are more supra-optimal than sunlit leaves. Model simulations for optimizing nitrogen distribution in C4 leaves show that under high light conditions, C4 plants over invest in carbon concentrating machinery and under invest in carboxylation machinery. A 20% redistribution in leaf nitrogen results in a 10% increase in leaf carbon assimilation without significant increases in transpiration under current CO2 concentrations of 400 ppm. Similarly, a 40% redistribution in leaf nitrogen results in a 15% increase in leaf carbon assimilation without significant increases in transpiration under future elevated CO2 concentrations of 550 ppm. Our model optimality simulations show that C4 leaves a supra optimal in their

Carbon-nitrogen feedbacks in the UVic ESCM

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R. Wania

2012-09-01

Full Text Available A representation of the terrestrial nitrogen cycle is introduced into the UVic Earth System Climate Model (UVic ESCM. The UVic ESCM now contains five terrestrial carbon pools and seven terrestrial nitrogen pools: soil, litter, leaves, stem and roots for both elements and ammonium and nitrate in the soil for nitrogen. Nitrogen cycles through plant tissue, litter, soil and the mineral pools before being taken up again by the plant. Biological N₂ fixation and nitrogen deposition represent external inputs to the plant-soil system while losses occur via leaching. Simulated carbon and nitrogen pools and fluxes are in the range of other models and observations. Gross primary production (GPP for the 1990s in the CN-coupled version is 129.6 Pg C a⁻¹ and net C uptake is 0.83 Pg C a⁻¹, whereas the C-only version results in a GPP of 133.1 Pg C a⁻¹ and a net C uptake of 1.57 Pg C a⁻¹. At the end of a transient experiment for the years 1800–1999, where radiative forcing is held constant but CO₂ fertilisation for vegetation is permitted to occur, the CN-coupled version shows an enhanced net C uptake of 1.05 Pg C a⁻¹, whereas in the experiment where CO₂ is held constant and temperature is transient the land turns into a C source of 0.60 Pg C a⁻¹ by the 1990s. The arithmetic sum of the temperature and CO₂ effects is 0.45 Pg C a⁻¹, 0.38 Pg C a⁻¹ lower than seen in the fully forced model, suggesting a strong nonlinearity in the CN-coupled version. Anthropogenic N deposition has a positive effect on Net Ecosystem Production of 0.35 Pg C a⁻¹. Overall, the UVic CN-coupled version shows similar characteristics to other CN-coupled Earth System Models, as measured by net C balance and sensitivity to changes in climate, CO₂ and temperature.

Impacts of revised PFTs on JULES simulated carbon and moisture fluxes

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Harper, Anna; Cox, Peter; Sitch, Stephen; Mercado, Lina; Luke, Catherine; Jupp, Tim; Wiltshire, Andy; Jones, Chris; Friedlingstein, Pierre

2013-04-01

JULES is the land surface model in the Hadley Centre GCM, which is used for investigations of climate and climate change. We analyze the impacts on the simulated carbon and moisture fluxes of extending the PFTs in a manner consistent with observed leaf traits. The model currently represents global vegetation with five PFTs (needleleaf and broadleaf trees, C3 and C4 grasses, and shrubs). We add three new PFTs to delineate between deciduous and evergreen trees and shrubs. Since the inception of JULES in the late 90's, a tremendous amount of new data linking leaf traits and potential photosynthesis is available. We use data from the TRY plant trait data base to revise the relationships between leaf area, leaf lifespan, leaf nitrogen content, and Vcmax. In addition, JULES now includes a canopy radiation scheme based on fractions of sunlit and shaded leaves at 10 levels in the canopy. This results in a vertical distribution of nitrogren and Vcmax through the canopy and enables multilayer scaling from leaf to canopy level photosynthesis. The scheme is more physically realistic than previous canopy radiation schemes, but remains to be evaluated outside of the Tropics. Within the constraints of observed values, we optimize new parameter values related to the canopy radiation and photosynthesis, using optimization software developed at the University of Exeter. Impacts on simulated GPP, respiration, and latent heat flux are examined. In particular, we are interested in a better understanding of carbon cycle dynamics in tropical forests. Using data from TRY, carbon fluxes are improved across all PFTs compared to observations from Fluxnet tower sites. We adopt a regional analysis to compare JULES fluxes in certain regions (e.g. tropical forests, and boreal and tropical shrub-dominated landscapes).

Influence of carbon dioxide content in the biogas to nitrogen oxides emissions

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Živković Marija A.

2010-01-01

Full Text Available Fuels derived from biomass are an alternative solution for the fossil fuel shortage. Usually this kind of fuels is called low calorific value fuels, due to the large proportion of inert components in their composition. The most common is carbon dioxide, and its proportion in biogas can be different, from 10 up to 40%, or even more. The presence of inert component in the composition of biogas causes the problems that are related with flame blow off limits. One of the possibilities for efficient combustion of biogas is the combustion in swirling flow including a pilot burner, aimed to expand the borders of stable combustion. This paper presents an analysis of the influence of the carbon dioxide content to the nitrogen oxides emissions. Laboratory biogas was used with different content of CO2 (10, 20, 30 and 40%. Investigation was carried out for different nominal powers, coefficients of excess air and carbon dioxide content. With increasing content of carbon dioxide, emission of nitrogen oxides was reduced, and this trend was the same throughout the whole range of excess air, carried out through measurements. Still, the influence of carbon dioxide content is significantly less than the influence of excess air. The coefficient of excess air greatly affects the production of radicals which are essential for the formation of nitrogen oxides, O, OH and CH. Also, the results show that the nominal power has no impact on the emission of nitrogen oxides.

Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

Science.gov (United States)

Wang, Fanan; Xu, Jinming; Shao, Xianzhao; Su, Xiong; Huang, Yanqiang; Zhang, Tao

2016-02-08

The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitrogen deposition outweighs climatic variability in driving annual growth rate of canopy beech trees: Evidence from long-term growth reconstruction across a geographic gradient.

Science.gov (United States)

Gentilesca, Tiziana; Rita, Angelo; Brunetti, Michele; Giammarchi, Francesco; Leonardi, Stefano; Magnani, Federico; van Noije, Twan; Tonon, Giustino; Borghetti, Marco

2018-07-01

In this study, we investigated the role of climatic variability and atmospheric nitrogen deposition in driving long-term tree growth in canopy beech trees along a geographic gradient in the montane belt of the Italian peninsula, from the Alps to the southern Apennines. We sampled dominant trees at different developmental stages (from young to mature tree cohorts, with tree ages spanning from 35 to 160 years) and used stem analysis to infer historic reconstruction of tree volume and dominant height. Annual growth volume (G V ) and height (G H ) variability were related to annual variability in model simulated atmospheric nitrogen deposition and site-specific climatic variables, (i.e. mean annual temperature, total annual precipitation, mean growing period temperature, total growing period precipitation, and standard precipitation evapotranspiration index) and atmospheric CO 2 concentration, including tree cambial age among growth predictors. Generalized additive models (GAM), linear mixed-effects models (LMM), and Bayesian regression models (BRM) were independently employed to assess explanatory variables. The main results from our study were as follows: (i) tree age was the main explanatory variable for long-term growth variability; (ii) GAM, LMM, and BRM results consistently indicated climatic variables and CO 2 effects on G V and G H were weak, therefore evidence of recent climatic variability influence on beech annual growth rates was limited in the montane belt of the Italian peninsula; (iii) instead, significant positive nitrogen deposition (N dep ) effects were repeatedly observed in G V and G H ; the positive effects of N dep on canopy height growth rates, which tended to level off at N dep values greater than approximately 1.0 g m -2  y -1 , were interpreted as positive impacts on forest stand above-ground net productivity at the selected study sites. © 2018 John Wiley & Sons Ltd.

Carbon sequestration and Jerusalem artichoke biomass under nitrogen applications in coastal saline zone in the northern region of Jiangsu, China

International Nuclear Information System (INIS)

Niu, Li; Manxia, Chen; Xiumei, Gao; Xiaohua, Long; Hongbo, Shao; Zhaopu, Liu; Zed, Rengel

2016-01-01

Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in g urea m"− "2): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419 g C kg"− "1. Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0–10 cm than 10–20 cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied. - Highlights: • Dry matter accumulation increased under nitrogen fertilization application. • Carbon density in Jerusalem artichoke ranged from 336 to 419 g C kg"− "1. • Soil carbon storage increased under nitrogen fertilizer application. • Nitrogen application is effective in increasing carbon sequestration.

Carbon sequestration and Jerusalem artichoke biomass under nitrogen applications in coastal saline zone in the northern region of Jiangsu, China

Energy Technology Data Exchange (ETDEWEB)

Niu, Li; Manxia, Chen; Xiumei, Gao [Jiangsu Provincial Key Laboratory of Marine Biology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Xiaohua, Long, E-mail: longxiaohua@njau.edu.cn [Jiangsu Provincial Key Laboratory of Marine Biology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Hongbo, Shao, E-mail: shaohongbochu@126.com [Institute of Agro-biotechnology, Jiangsu Academy of Agriculture Sciences, Nanjing 210014 (China); Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003 (China); Zhaopu, Liu [Jiangsu Provincial Key Laboratory of Marine Biology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Zed, Rengel [Soil Science and Plant Nutrition, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

2016-10-15

Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in g urea m{sup −} {sup 2}): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419 g C kg{sup −} {sup 1}. Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0–10 cm than 10–20 cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied. - Highlights: • Dry matter accumulation increased under nitrogen fertilization application. • Carbon density in Jerusalem artichoke ranged from 336 to 419 g C kg{sup −} {sup 1}. • Soil carbon storage increased under nitrogen fertilizer application. • Nitrogen application is effective in increasing carbon sequestration.

Revealing the Origin of Activity in Nitrogen-Doped Nanocarbons towards Electrocatalytic Reduction of Carbon Dioxide.

Science.gov (United States)

Xu, Junyuan; Kan, Yuhe; Huang, Rui; Zhang, Bingsen; Wang, Bolun; Wu, Kuang-Hsu; Lin, Yangming; Sun, Xiaoyan; Li, Qingfeng; Centi, Gabriele; Su, Dangsheng

2016-05-23

Carbon nanotubes (CNTs) are functionalized with nitrogen atoms for reduction of carbon dioxide (CO2 ). The investigation explores the origin of the catalyst's activity and the role of nitrogen chemical states therein. The catalysts show excellent performances, with about 90 % current efficiency for CO formation and stability over 60 hours. The Tafel analyses and density functional theory calculations suggest that the reduction of CO2 proceeds through an initial rate-determining transfer of one electron to CO2 , which leads to the formation of carbon dioxide radical anion (CO2 (.-) ). The initial reduction barrier is too high on pristine CNTs, resulting in a very high overpotentials at which the hydrogen evolution reaction dominates over CO2 reduction. The doped nitrogen atoms stabilize the radical anion, thereby lowering the initial reduction barrier and improving the intrinsic activity. The most efficient nitrogen chemical state for this reaction is quaternary nitrogen, followed by pyridinic and pyrrolic nitrogen. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitrogen deficiency detection using reflected shortwave radiation from irrigated corn canopies

International Nuclear Information System (INIS)

Blackmer, T.M.; Schepers, J.S.; Varvel, G.E.; Walter-Shea, E.A.

1996-01-01

Techniques that measure the N status of corn (Zea mays L.) can aid in management decisions that have economic and environmental implications. This study was conducted to identify reflected electromagnetic wavelengths most sensitive to detecting N deficiencies in a corn canopy with the possibility for use as a management tool. Reflected shortwave radiation was measured from an irrigated corn N response trial with four hybrids and five N rates at 0, 40, 80, 120, and 160 kg N ha -1 in 1992 and 0, 50, 100, 150, and 200 kg N ha -1 in 1993. A portable spectroradiometer was used to measure reflected radiation (400-1100 nm in 1992, 350-1050 nm in 1993) from corn canopies at approximately the R5 growth stage. Regression analyses revealed that reflected radiation near 550 and 710 nm was superior to reflected radiation near 450 or 650 nm for detecting N deficiencies. The ratio of light reflectance between 550 and 600 nm to light reflectance between 800 and 900 nm also provided sensitive detection of N stress. In 1993, an inexpensive photometric cell, which has peak sensitivity to light centered at 550 nm, was also used to measure reflected radiation from a corn canopy. Photometric cell readings correlated with relative grain yield (P < 0.001, r 2 = 0.74), but more research will be required to develop procedures to account for varying daylight conditions. These results provide information needed for the development of variable-rate fertilizer N application technology. (author)

The Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS: model description and application to a temperate deciduous forest canopy

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R. D. Saylor

2013-01-01

Full Text Available Forest canopies are primary emission sources of biogenic volatile organic compounds (BVOCs and have the potential to significantly influence the formation and distribution of secondary organic aerosol (SOA mass. Biogenically-derived SOA formed as a result of emissions from the widespread forests across the globe may affect air quality in populated areas, degrade atmospheric visibility, and affect climate through direct and indirect forcings. In an effort to better understand the formation of SOA mass from forest emissions, a 1-D column model of the multiphase physical and chemical processes occurring within and just above a vegetative canopy is being developed. An initial, gas-phase-only version of this model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS, includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer (PBL, near-explicit representation of chemical transformations, mixing with the background atmosphere and bi-directional exchange between the atmosphere and canopy and the atmosphere and forest floor. The model formulation of ACCESS is described in detail and results are presented for an initial application of the modeling system to Walker Branch Watershed, an isoprene-emission-dominated forest canopy in the southeastern United States which has been the focal point for previous chemical and micrometeorological studies. Model results of isoprene profiles and fluxes are found to be consistent with previous measurements made at the simulated site and with other measurements made in and above mixed deciduous forests in the southeastern United States. Sensitivity experiments are presented which explore how canopy concentrations and fluxes of gas-phase precursors of SOA are affected by background anthropogenic nitrogen oxides (NO_x. Results from these experiments suggest that the

Synthesis of 2D Nitrogen-Doped Mesoporous Carbon Catalyst for Oxygen Reduction Reaction

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Zhipeng Yu

2017-02-01

Full Text Available 2D nitrogen-doped mesoporous carbon (NMC is synthesized by using a mesoporous silica film as hard template, which is then investigated as a non-precious metal catalyst for the oxygen reduction reaction (ORR. The effect of the synthesis conditions on the silica template and carbon is extensively investigated. In this work, we employ dual templates—viz. graphene oxide and triblock copolymer F127—to control the textural features of a 2D silica film. The silica is then used as a template to direct the synthesis of a 2D nitrogen-doped mesoporous carbon. The resultant nitrogen-doped mesoporous carbon is characterized by transmission electron microscopy (TEM, nitrogen ad/desorption isotherms, X-ray photoelectron spectroscopy (XPS, cyclic voltammetry (CV, and rotating disk electrode measurements (RDE. The electrochemical test reveals that the obtained 2D-film carbon catalyst yields a highly electrochemically active surface area and superior electrocatalytic activity for the ORR compared to the 3D-particle. The superior activity can be firstly attributed to the difference in the specific surface area of the two catalysts. More importantly, the 2D-film morphology makes more active sites accessible to the reactive species, resulting in a much higher utilization efficiency and consequently better activity. Finally, it is noted that all the carbon catalysts exhibit a higher ORR activity than a commercial Pt catalyst, and are promising for use in fuel cells.

Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

Science.gov (United States)

Levicán, Gloria; Ugalde, Juan A; Ehrenfeld, Nicole; Maass, Alejandro; Parada, Pilar

2008-01-01

Background Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments. Results In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air. Conclusion The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms. PMID:19055775

Regulation of Carbon Flow by Nitrogen and Light in the Red Alga, Gelidium coulteri.

Science.gov (United States)

Macler, B A

1986-09-01

The red alga Gelidium coulteri Harv. photosynthetically fixed [(14)C] bicarbonate at high rates under defined conditions in unialgal laboratory culture. The fixation rate and flow of photosynthate into various end products were dependent on the nitrogen status of the tissue. Plants fed luxury levels of nitrogen (approximately 340 micromolar) showed fixation rates several-fold higher than those seen for plants starved for nitrogen. The addition of NO(3) (-) or NH(4) (+) to such starved plants further inhibited fixation over at least the first several hours after addition. The majority of (14)C after incubations of 30 minutes to 8 hours was found in the compounds floridoside, agar and floridean starch. In addition, amino acids and intermediate compounds of the reductive pentose phosphate pathway, glycolytic pathway and tricarboxylic acid cycle were detected. Nitrogen affected the partitioning of labeled carbon into these compounds. Plants under luxury nitrogen conditions had higher floridoside levels and markedly lower amounts of agar and starch than found in plants limited for nitrogen. Amino acid, phycobiliprotein and chlorophyll levels were also significantly higher in nitrogen-enriched plants. Addition of NO(3) (-) to starved plants led to an increase in floridoside, tricarboxylic acid cycle intermediates and amino acids within 1 hour and inhibited carbon flow into agar and starch. Carbon fixation in the dark was only 1 to 7% of that seen in the light. Dark fixation of [(14)C]bicarbonate yielded label primarily in tricarboxylic acid cycle intermediates, amino acids and polysaccharides. Nitrogen stimulated amino acid synthesis at the expense of agar and starch. Floridoside was only a minor component in the dark. Pulse-chase experiments, designed to show carbon turnover, indicated a 2-fold increase in labeling of agar over 96 hours of chase in the light. No increases were seen in the dark. Low molecular weight pools, including floridoside, decreased 2- to 5-fold

Intra-Urban Variability in Elemental Carbon Deposition to Tree Canopies

Science.gov (United States)

Barrett, T. E.; Ponette-González, A.; Rindy, J. E.; Sheesley, R. J.

2017-12-01

Urban areas cover biomass combustion, EC is a powerful climate-forcing agent and a significant component of fine particulate matter in urban atmospheres. Thus, understanding the factors that govern EC removal in urban areas could help mitigate climate change, while improving air quality for urban residents. EC particles can be removed from the atmosphere in precipitation (wet and fog deposition) or they can settle directly onto receptor surfaces (dry deposition). Only limited measurements indicate that EC deposition is higher in urban than in rural and remote regions. However, EC deposition likely exhibits considerable intra-urban variability, with tree canopies serving as potentially important sinks for EC on the cityscape. The goal of this research is to quantify spatial variability in total (wet + dry) EC deposition to urban tree canopies in the Dallas-Fort Worth Metroplex. Using a stratified non-random sampling design, 41 oak trees (22 post oak (Quercus stellata) and 19 live oak (Quercus virginiana)) were selected near (100 m) for measurements of throughfall (water that falls from the canopy to the forest floor). Additionally, 16 bulk rainfall samplers were deployed in grassy areas with no canopy cover. Results from one rain event indicate a volume weighted mean concentration of 83 µg EC L-1 in post oak throughfall, 36 µg EC L-1 in live oak throughfall, and 4 µg EC L-1 in bulk rainfall. Total EC deposition to oak tree canopies was 2.0 ± 2.1 (SD) mg m-2 for post oak and 0.7 ± 0.3 mg m-2 for live oak. Bulk rainfall deposition was 0.08 ± 0.1 mg m-2. Our preliminary findings show that trees are effective urban air filters, removing 9-25 times more EC from the atmosphere than rainwater alone. Resolving surface controls on atmospheric EC removal is key to developing and assessing near-term climate and air quality mitigation strategies.

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q.J. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Chen, X. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Ostrikov, K., E-mail: kostya.ostrikov@csiro.au [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2011-09-22

Highlights: > A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. > The carbon nanotubes are later treated with nitrogen plasmas. > The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. > A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 {mu}A/cm{sup 2}) achieved at a low applied field (3.50 V/{mu}m) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

International Nuclear Information System (INIS)

Wang, B.B.; Cheng, Q.J.; Chen, X.; Ostrikov, K.

2011-01-01

Highlights: → A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. → The carbon nanotubes are later treated with nitrogen plasmas. → The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. → A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 μA/cm 2 ) achieved at a low applied field (3.50 V/μm) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Estimates of forest canopy height and aboveground biomass using ICESat.

Science.gov (United States)

Michael A. Lefsky; David J. Harding; Michael Keller; Warren B. Cohen; Claudia C. Carabajal; Fernando Del Bom; Maria O. Hunter; Raimundo Jr. de Oliveira

2005-01-01

Exchange of carbon between forests and the atmosphere is a vital component of the global carbon cycle. Satellite laser altimetry has a unique capability for estimating forest canopy height, which has a direct and increasingly well understood relationship to aboveground carbon storage. While the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land...

El Niño drought increased canopy turnover in Amazon forests.

Science.gov (United States)

Leitold, Veronika; Morton, Douglas C; Longo, Marcos; Dos-Santos, Maiza Nara; Keller, Michael; Scaranello, Marcos

2018-03-25

Amazon droughts, including the 2015-2016 El Niño, may reduce forest net primary productivity and increase canopy tree mortality, thereby altering both the short- and the long-term net forest carbon balance. Given the broad extent of drought impacts, inventory plots or eddy flux towers may not capture regional variability in forest response to drought. We used multi-temporal airborne Lidar data and field measurements of coarse woody debris to estimate patterns of canopy turnover and associated carbon losses in intact and fragmented forests in the central Brazilian Amazon between 2013-2014 and 2014-2016. Average annualized canopy turnover rates increased by 65% during the drought period in both intact and fragmented forests. The average size and height of turnover events was similar for both time intervals, in contrast to expectations that the 2015-2016 El Niño drought would disproportionally affect large trees. Lidar-biomass relationships between canopy turnover and field measurements of coarse woody debris were modest (R 2  ≈ 0.3), given similar coarse woody debris production and Lidar-derived changes in canopy volume from single tree and multiple branch fall events. Our findings suggest that El Niño conditions accelerated canopy turnover in central Amazon forests, increasing coarse woody debris production by 62% to 1.22 Mg C ha -1  yr -1 in drought years . No claim to original US Government works New Phytologist © 2018 New Phytologist Trust.

Direct synthesis of nitrogen-containing carbon nanotubes on carbon paper for fuel cell electrode

Science.gov (United States)

Yin, Wong Wai; Daud, Wan Ramli Wan; Mohamad, Abu Bakar; Kadhum, Abdul Amir Hassan; Majlan, Edy Herianto; Shyuan, Loh Kee

2012-06-01

Organic catalyst has recently been identified as the potential substitution for expensive platinum electrocatalyst for fuel cell application. Numerous studies have shown that the nitrogen-containing carbon nanotubes (N-CNT) can be synthesized through spray pyrolysis or floating chemical vapor deposition (CVD) technique using various type of organometallic as precursors. This paper presents the method of synthesis and the initial findings of the growth of N-CNT directly on carbon paper using a modified CVD technique. In this research, nickel (II) phthalocyanines (Ni-Pc) as precursor was dissolved in ethanol solvent, stirred and sonicated to become homogenized. The solution was poured into a bubbler and heated up to allow the mixture to vaporize. Subsequently, the solution vapor was flowed into the tubical reactor maintained at 900°C. Carbon paper sputtered with nickel nanoparticles was used as the substrate. The synthesized sample was examined through Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM) and Fourier Transform Infra-Red (FTIR). Long, entangled and compartmentalized nanotubes with tube diameter ranging 23-27 nm were found covered the carbon paper surface with approximate of 5.5-6.0 μm in thickness. EDX analysis has successfully showed the presence of nitrogen in the carbon nanotube. FTIR analysis showed the presence of the C-N bond on CNT.

Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes

Czech Academy of Sciences Publication Activity Database

Kopáček, Jiří; Cosby, B. J.; Evans, C. D.; Hruška, J.; Moldan, F.; Oulehle, F.; Šantrůčková, H.; Tahovská, K.; Wright, R. F.

2013-01-01

Roč. 115, 1-3 (2013), s. 33-51 ISSN 0168-2563. [BIOGEOMON : international symposium on ecosystem behavior /7./. Northport, 15.07.2012-20.07.2012] R&D Projects: GA ČR(CZ) GAP504/12/1218 Institutional support: RVO:60077344 Keywords : nitrogen * carbon * sulphur * acidification * forest soil * modelling Subject RIV: DJ - Water Pollution ; Quality Impact factor: 3.730, year: 2013

Carbon and nitrogen burial in a plateau lake during eutrophication and phytoplankton blooms.

Science.gov (United States)

Huang, Changchun; Zhang, Linlin; Li, Yunmei; Lin, Chen; Huang, Tao; Zhang, Mingli; Zhu, A-Xing; Yang, Hao; Wang, Xiaolei

2018-03-01

Organic carbon (OC) buried in lake sediment is an important component of the global carbon cycle. The impact of eutrophication on OC burial in lakes should be addressed due to worldwide lake eutrophication. Fourteen 210 Pb- and 137 Cs-dated sediment cores taken in Dianchi Lake (China) in August 2006 (seven cores) and July 2014 (seven cores) were analyzed to evaluate the response of the organic carbon accumulation rate (OCAR) to eutrophication and algal blooms over the past hundred years. The mean value of OCAR before eutrophication occurred in 1979, 16.62±7.53 (mean value±standard deviation), increased to 54.33±27.29gm -2 yr -1 after eutrophication. It further increased to 61.98±28.94gm -2 yr -1 after algal blooms occurred (1989). The accumulation rate of organic nitrogen (ONAR) is coupled with OCAR. The high loss rate of OC and organic nitrogen (ON) leads to a long-term burial efficiency of only 10% and 5% of OC and ON. However, this efficiency can still lead to an increase in OCAR by a factor of 4.55 during algal blooms in Dianchi Lake. Dianchi Lake stored 1.26±0.32 Tg carbon and 0.071±0.018 Tg nitrogen, including 0.94±0.23 Tg OC and 0.32±0.14 Tg inorganic carbon, 0.066±0.018 Tg ON, 0.002±0.001 Tg nitrate nitrogen (NO 3 -N) and 0.003±0.001 Tg ammonium nitrogen (NH 4 -N) between 1900 and 2012. Copyright © 2017 Elsevier B.V. All rights reserved.

Nitrogen Doped Ordered Mesoporous Carbon as Support of PtRu Nanoparticles for Methanol Electro-Oxidation

Directory of Open Access Journals (Sweden)

David Sebastián

2018-04-01

Full Text Available The low oxidation kinetics of alcohols and the need for expensive platinum group metals are still some of the main drawbacks for the commercialization of energy efficient direct alcohol fuel cells. In this work, we investigate the influence of nitrogen doping of ordered mesoporous carbon (CMK as support on the electrochemical activity of PtRu nanoparticles. Nitrogen doping procedures involve the utilization of pyrrole as both nitrogen and carbon precursor by means of a templating method using mesoporous silica. This method allows obtaining carbon supports with up to 14 wt. % nitrogen, with an effective introduction of pyridinic, pyrrolic and quaternary nitrogen. PtRu nanoparticles were deposited by sodium formate reduction method. The presence of nitrogen mainly influences the Pt:Ru atomic ratio at the near surface, passing from 50:50 on the bare (un-doped CMK to 70:30 for the N-doped CMK catalyst. The electroactivity towards the methanol oxidation reaction (MOR was evaluated in acid and alkaline electrolytes. The presence of nitrogen in the support favors a faster oxidation of methanol due to the enrichment of Pt at the near surface together with an increase of the intrinsic activity of PtRu nanoparticles.

Novel porous carbon materials with ultrahigh nitrogen contents for selective CO 2 capture

KAUST Repository

Zhao, Yunfeng; Zhao, Lan; Yao, Kexin; Yang, Yang; Zhang, Qiang; Han, Yu

2012-01-01

Nitrogen-doped carbon materials were prepared by a nanocasting route using tri-continuous mesoporous silica IBN-9 as a hard template. Rationally choosing carbon precursors and carefully controlling activation conditions result in an optimized material denoted as IBN9-NC1-A, which possesses a very high nitrogen doping concentration (∼13 wt%) and a large surface area of 890 m 2 g -1 arising from micropores (<1 nm). It exhibits an excellent performance for CO 2 adsorption over a wide range of CO 2 pressures. Specifically, its equilibrium CO 2 adsorption capacity at 25 °C reaches up to 4.50 mmol g -1 at 1 bar and 10.53 mmol g -1 at 8 bar. In particular, it shows a much higher CO 2 uptake at low pressure (e.g. 1.75 mmol g -1 at 25 °C and 0.2 bar) than any reported carbon-based materials, owing to its unprecedented nitrogen doping level. The high nitrogen contents also give rise to significantly enhanced CO 2/N 2 selectivities (up to 42), which combined with the high adsorption capacities, make these new carbon materials promising sorbents for selective CO 2 capture from power plant flue gas and other relevant applications. © 2012 The Royal Society of Chemistry.

Nitrogen-doping effects on the growth, structure and electrical performance of carbon nanotubes obtained by spray pyrolysis method

Energy Technology Data Exchange (ETDEWEB)

Ionescu, Mihnea Ioan; Zhang Yong; Li Ruying [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON N6A 5B9 (Canada); Abou-Rachid, Hakima [Defense Research and Development Canada - Valcartier, 2459 Boulevard PieXI Nord, Quebec, QC G3J 1X5 (Canada); Sun Xueliang, E-mail: xsun@eng.uwo.ca [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON N6A 5B9 (Canada)

2012-03-01

Vertically aligned nitrogen-doped carbon nanotubes (CNTs) with modulated nitrogen content have been synthesized in a large scale by using spray pyrolysis chemical vapor deposition technique. The effects of nitrogen doping on the growth, structure and electrical performance of carbon nanotubes have been systematically examined. Field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman techniques have been employed to characterize the morphology, composition, and vibrational properties of nanotubes. The results indicate that the nitrogen incorporation significantly influences the growth rate, morphology, size and structure of nanotubes. Electrical measurement investigation of the nanotubes indicates that the change in electrical resistance increases with temperature and pressure as the nitrogen concentration increases inside the tubes. This work presents a versatile, safe, and easy way to scale up route of growing carbon nanotubes with controlled nitrogen content and modulated structure, and may provide an insight in developing various nitrogen-doped carbon-based nanodevices.

Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

Directory of Open Access Journals (Sweden)

Ehrenfeld Nicole

2008-12-01

Full Text Available Abstract Background Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments. Results In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air. Conclusion The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.

A mobile light source for carbon/nitrogen cameras

International Nuclear Information System (INIS)

Trower, W.P.; Melekhin, V.N.; Shvedunov, V.I.; Sobenin, N.P.

1995-01-01

The pulsed light source for carbon/nitrogen cameras developed to image concealed narcotics/explosives is described. This race-track microtron will produce 40 mA pulses of 70 MeV electrons, have minimal size and weight, and maximal ruggedness and reliability, so that it can be transported on a truck. (orig.)

A mobile light source for carbon/nitrogen cameras

Science.gov (United States)

Trower, W. P.; Karev, A. I.; Melekhin, V. N.; Shvedunov, V. I.; Sobenin, N. P.

1995-05-01

The pulsed light source for carbon/nitrogen cameras developed to image concealed narcotics/explosives is described. This race-track microtron will produce 40 mA pulses of 70 MeV electrons, have minimal size and weight, and maximal ruggedness and reliability, so that it can be transported on a truck.

Ruthenium supported on nitrogen-doped carbon nanotubes for the oxygen reduction reaction in alkaline electrolyte; Poster

CSIR Research Space (South Africa)

Mabena, LF

2012-07-01

Full Text Available . Recently, several researchers have shown that nitrogen modified carbon nanotubes (CNTs) are good electrocatalyst supports and that they enhance the electrocatalytic activity for the ORR. Nitrogen-doped carbon nanotubes (N-CNTs) prepared via thermal chemical...

Modeling Water and Nutrient Transport through the Soil-Root-Canopy Continuum: Explicitly Linking the Below- and Above-Ground Processes

Science.gov (United States)

Kumar, P.; Quijano, J. C.; Drewry, D.

2010-12-01

results using coupled partial differential equations of transport in soils and roots along with that for nutrient dynamics. We study the feedbkack of HR on the dynamics of water and nitrogen cycling in the soil and how these dynamics influence root water and nitrogen uptake and consequently carbon assimilation by the canopy. The forcing data is obtained from the Ameriflux Tower located in Blodgett Forest, Sierra Nevada, California. We consider single-species (Ponderosa Pine) and multi-species (overstory Ponderosa Pine and understory shrubs) interaction. When single species is considered, the near surface soil-moisture available from HR during dry summer season is an important source of evaporation and contributes significantly to the total ET flux. However, when multi-species interactions are taken into account, the soil-water from the HR becomes an important source of transpiration from the understory. The results also show that passive plant nitrogen uptake is higher when HR is present and it is critical for sustaining expected rates of carbon assimilation.

Short and long-term impacts of nitrogen deposition on carbon sequestration by forest ecosystems

NARCIS (Netherlands)

Vries, de W.; Du, E.; Butterbach-Bahl, K.

2014-01-01

The carbon to nitrogen response of forest ecosystems depends on the possible occurrence of nitrogen limitation versus possible co-limitations by other drivers, such as low temperature or availability of phosphorus. A combination of nitrogen retention estimates and stoichiometric scaling is used to

Adsorption/oxidation of hydrogen sulfide on nitrogen-containing activated carbons

Energy Technology Data Exchange (ETDEWEB)

Adib, F.; Bagreev, A.; Bandosz, T.J.

2000-02-22

Wood-based activated carbon was modified by impregnation with urea and heat treatment at 450 and 950 C. The chemical and physical properties of materials were determined using acid/base titration, FTIR, thermal analysis, IGC, and sorption of nitrogen. The surface features were compared to those of a commercial urea-modified carbon. Then, the H{sub 2}S breakthrough capacity tests were carried out, and the sorption capacity was evaluated. The results showed that urea-modified sorbents have a capacity similar to that of the received material; however, the conversion of hydrogen sulfide to a water-soluble species is significantly higher. It happens due to a high dispersion of basic nitrogen compounds in the small pores of carbons, where oxidation of hydrogen sulfide ions to sulfur radicals followed by the creation of sulfur oxides and sulfuric acid occurs. It is proposed that the process proceeds gradually, from small pores to larger, and that the degree of microporosity is an important factor.

The difference in thermal and mechanical stabilities of austenite between carbon- and nitrogen-added metastable austenitic stainless steels

International Nuclear Information System (INIS)

Masumura, Takuro; Nakada, Nobuo; Tsuchiyama, Toshihiro; Takaki, Setsuo; Koyano, Tamotsu; Adachi, Kazuhiko

2015-01-01

In order to evaluate the effects of carbon and nitrogen addition on the stability of austenite, athermal and deformation-induced α′-martensitic transformation behaviors were investigated using type 304-metastable austenitic stainless steels containing 0.1 mass% carbon or nitrogen. The difference in the development of the deformation microstructure in particular is discussed in terms of the stacking-fault energy (SFE). Since carbon-added steel has a lower SFE than that of nitrogen-added steel, deformation twins and ε-martensite were preferentially formed in the carbon-added steel, whereas a dislocation cell structure developed in the nitrogen-added steel. Crystallographic analysis using the electron backscatter diffraction method revealed that the difference in the deformation microstructure has a significant influence on the growth behavior of deformation-induced α′-martensite, that is, the interface of the deformation twins and ε-martensite suppresses the growth of α′-martensite, whereas dislocation cell boundaries are not effective. As a result, the mechanical stability of carbon-added steel is slightly higher than that of nitrogen-added steel, although the thermal stabilization effect of carbon is much lower than that of nitrogen

High-capacitance supercapacitors using nitrogen-decorated porous carbon derived from novolac resin containing peptide linkage

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Jung [Institute of Carbon Science and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Jang, In Young; Park, Ki Chul; Jung, Yong Chae; Oka, Takuyuki [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Iinou, Satoshi [MEFS, Co. Ltd. Choei Nagano, Higasiguchi Bldg, 2F, 1000-1 Gentakubo, Kurita, Nagano 380-0921 (Japan); Komori, Yasuhiro; Kozutsumi, Toshihiko; Hashiba, Takashi [SHOWA HIGHPOLYMER, Co., Ltd. 1021 Tomizuka-cho, Isesaki-City, Gunma 372-0833 (Japan); Kim, Yoong Ahm, E-mail: yak@endomoribu.shinshu-u.ac.j [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Endo, Morinobu [Institute of Carbon Science and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)] [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)

2010-08-01

We fabricated nitrogen-decorated porous carbon exhibiting high capacitance per unit volume and unit weight via chemical activation of novolac resin containing peptide linkage. The porosity and the amount of nitrogen atoms were controlled by changing the molecular weight of novolac resin, the added amount of potassium hydroxide, or both. After chemical activation, positively charged nitrogen atoms (i.e., pyridine/pyrrole) at 400.3 eV in photoemission spectra contributed to both a shift in the point of zero charge toward negative potential and the generation of pseudocapacitance. Suitably developed pores and the positively charged nitrogen atoms make nitrogen-decorated novolac resin-derived porous carbon a promising material for electrodes in high-performance supercapacitors.

Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces

Directory of Open Access Journals (Sweden)

Shaena Montanari

2017-06-01

Full Text Available Stable isotope analysis of feces can provide a non-invasive method for tracking the dietary habits of nearly any mammalian species. While fecal samples are often collected for macroscopic and genetic study, stable isotope analysis can also be applied to expand the knowledge of species-specific dietary ecology. It is somewhat unclear how digestion changes the isotope ratios of animals’ diets, so more controlled diet studies are needed. To date, most diet-to-feces controlled stable isotope experiments have been performed on herbivores, so in this study I analyzed the carbon and nitrogen stable isotope ratios in the diet and feces of the meerkat (Suricata suricatta, a small omnivorous mammal. The carbon trophic discrimination factor between diet and feces (Δ13Cfeces is calculated to be 0.1 ± 1.5‰, which is not significantly different from zero, and in turn, not different than the dietary input. On the other hand, the nitrogen trophic discrimination factor (Δ15Nfeces is 1.5 ± 1.1‰, which is significantly different from zero, meaning it is different than the average dietary input. Based on data generated in this experiment and a review of the published literature, carbon isotopes of feces characterize diet, while nitrogen isotope ratios of feces are consistently higher than dietary inputs, meaning a discrimination factor needs to be taken into account. The carbon and nitrogen stable isotope values of feces are an excellent snapshot of diet that can be used in concert with other analytical methods to better understand ecology, diets, and habitat use of mammals.

Benthic biogeochemical cycling, nutrient stoichiometry, and carbon and nitrogen mass balances in a eutrophic freshwater bay

Science.gov (United States)

Klump, J.V.; Fitzgerald, S.A.; Waplesa, J.T.

2009-01-01

Green Bay, while representing only ,7% of the surface area and ??1.4% of the volume of Lake Michigan, contains one-third of the watershed of the lake, and receives approximately one-third of the total nutrient loading to the Lake Michigan basin, largely from the Fox River at the southern end of the bay. With a history of eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments accumulating at up to 1 cm per year. Depositional fluxes of organic matter varied from ??0.1 mol C m-2 yr-1 to >10 mol C m-2 yr-1 and were both fairly uniform in stoichiometric composition and relatively labile. Estimates of benthic recycling derived from pore-water concentration gradients, whole-sediment incubation experiments, and deposition-burial models of early diagenesis yielded an estimated 40% of the carbon and 50% of the nitrogen recycled back into the overlying water. Remineralization was relatively rapid with ??50% of the carbon remineralized within <15 yr of deposition, and a mean residence time for metabolizable carbon and nitrogen in the sediments of 20 yr. On average, organic carbon regeneration occurred as 75% CO2, 15% CH4, and 10% dissolved organic carbon (DOC). Carbon and nitrogen budgets for the southern bay were based upon direct measurements of inputs and burial and upon estimates of export and production derived stoichiometrically from a coupled phosphorus budget. Loadings of organic carbon from rivers were ??3.7 mol m-2 yr-1, 80% in the form of DOC and 20% as particulate organic carbon. These inputs were lost through export to northern Green Bay and Lake Michigan (39%), through sediment burial (26%), and net CO2 release to the atmosphere (35%). Total carbon input, including new production, was 4.54 mol m-2 C yr-1, equivalent to ??10% of the gross annual primary production. Nitrogen budget terms were less well quantified

Radiative transfer within seagrass canopies: impact on carbon budgets and light requirements

Science.gov (United States)

Zimmerman, Richard C.; Mobley, Curtis D.

1997-02-01

Seagrasses are ecologically important but extremely vulnerable to anthropogenic modifications of the coastal zone that affect light availability within these unique ecosystems. Strongly pigmented seagrass leaves can extend for more than 1 m above the substrate and biomass is distributed unevenly throughout the canopy. in this study, light attenuation in a 7 m water column that contained a seagrass canopy extending 1.5 m above the bottom was calculated by the radiative transfer model Hydrolight using the spectral absorbance of eelgrass leaves and a non-uniform vertical distribution of biomass. Runs were performed in clear and turbid water columns, over san d and mud substrates, and with shoot densities ranging from 25 to 200 m-2 using solar angles for both winter and summer solstices. The flux of photosynthetically active irradiance (EPAR) reaching the top of the seagrass canopy was twice as high in summer compared to winter, and in clear water compared to turbid water. Sediment type had a measurable effect on EPAR only within the bottom third of the canopy. Light penetration within the canopy was inversely proportional to shoot density. Introduction of daylength and a sinusoidal distribution of EPAR throughout the day greatly increased the importance of solar elevation on daily integrated production relative to water column turbidity and sediment type. Shoot-specific productivity decreased and the position of maximum shoot productivity within the canopy shallowed as shoot density increased. Positive net photosynthesis for entire shoots was possible only when plant density was lower than 100 shoots m-2 in winter; values consistent with field observations. Although very simplistic with regard to inherent optical properties of real seagrass leaves, this model was able to generate estimates of maximum sustainable shoot density that were fully testable by, and wholly consistent with, field observations.

The influence of various carbon and nitrogen sources on oil production by Fusarium oxysporum.

Science.gov (United States)

Joshi, S; Mathur, J M

1987-01-01

The oil-synthesizing capacity of Fusarium oxysporum, cultivated on basal nutrient medium, was evaluated using different carbon and nitrogen sources. In one of the media, molasses was also used as a principal carbon source. Media containing glucose and ammonium nitrate were found to be most efficient for oil production. Fatty acid profile of the fungal oil indicated the presence of a wide range of fatty acids ranging from C8 to C24. Fatty acid composition largely depends on the type of carbon and nitrogen sources.

Biomass derived nitrogen-doped hierarchical porous carbon sheets for supercapacitors with high performance.

Science.gov (United States)

Wang, Cunjing; Wu, Dapeng; Wang, Hongju; Gao, Zhiyong; Xu, Fang; Jiang, Kai

2018-08-01

A facile potassium chloride salt-locking technique combined with hydrothermal treatment on precursors was explored to prepare nitrogen-doped hierarchical porous carbon sheets in air from biomass. Benefiting from the effective synthesis strategy, the as-obtained carbon possesses a unique nitrogen-doped thin carbon sheet structure with abundant hierarchical pores and large specific surface areas of 1459 m 2  g -1 . The doped nitrogen in carbon framework has a positive effect on the electrochemical properties of the electrode material, the thin carbon sheet structure benefits for fast ion transfer, the abundant meso-pores provide convenient channels for rapid charge transportation, large specific surface area and lots of micro-pores guarantee sufficient ion-storage sites. Therefore, applied for supercapacitors, the carbon electrode material exhibits an outstanding specific capacitance of 451 F g -1 at 0.5 A g -1 in a three-electrode system. Moreover, the assembled symmetric supercapacitor based on two identical carbon electrodes also displays high specific capacitance of 309 F g -1 at 0.5 A g -1 , excellent rate capacity and remarkable cycling stability with 99.3% of the initial capacitance retention after 10,000 cycles at 5 A -1 . The synthesis strategy avoids expensive inert gas protection and the use of corrosive KOH and toxic ZnCl 2 activated reagents, representing a promising green route to design advanced carbon electrode materials from biomass for high-capacity supercapacitors. Copyright © 2018. Published by Elsevier Inc.

The production of cyanobacterial carbon under nitrogen-limited cultivation and its potential for nitrate removal.

Science.gov (United States)

Huang, Yingying; Li, Panpan; Chen, Guiqin; Peng, Lin; Chen, Xuechu

2018-01-01

Harmful cyanobacterial blooms (CyanoHABs) represent a serious threat to aquatic ecosystems. A beneficial use for these harmful microorganisms would be a promising resolution of this urgent issue. This study applied a simple method, nitrogen limitation, to cultivate cyanobacteria aimed at producing cyanobacterial carbon for denitrification. Under nitrogen-limited conditions, the common cyanobacterium, Microcystis, efficiently used nitrate, and had a higher intracellular C/N ratio. More importantly, organic carbons easily leached from its dry powder; these leachates were biodegradable and contained a larger amount of dissolved organic carbon (DOC) and carbohydrates, but a smaller amount of dissolved total nitrogen (DTN) and proteins. When applied to an anoxic system with a sediment-water interface, a significant increase of the specific NO X - -N removal rate was observed that was 14.2 times greater than that of the control. This study first suggests that nitrogen-limited cultivation is an efficient way to induce organic and carbohydrate accumulation in cyanobacteria, as well as a high C/N ratio, and that these cyanobacteria can act as a promising carbon source for denitrification. The results indicate that application as a carbon source is not only a new way to utilize cyanobacteria, but it also contributes to nitrogen removal in aquatic ecosystems, further limiting the proliferation of CyanoHABs. Copyright © 2017. Published by Elsevier Ltd.

Heavily Graphitic-Nitrogen Self-doped High-porosity Carbon for the Electrocatalysis of Oxygen Reduction Reaction

Science.gov (United States)

Feng, Tong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Shi, Dongping; Guo, Chaozhong; Huang, Yu; Wang, Yi; Cheng, Jing; Li, Yanrong; Diao, Qizhi

2017-11-01

Large-scale production of active and stable porous carbon catalysts for oxygen reduction reaction (ORR) from protein-rich biomass became a hot topic in fuel cell technology. Here, we report a facile strategy for synthesis of nitrogen-doped porous nanocarbons by means of a simple two-step pyrolysis process combined with the activation of zinc chloride and acid-treatment process, in which kidney bean via low-temperature carbonization was preferentially adopted as the only carbon-nitrogen sources. The results show that this carbon material exhibits excellent ORR electrocatalytic activity, and higher durability and methanol-tolerant property compared to the state-of-the-art Pt/C catalyst for the ORR, which can be mainly attributed to high graphitic-nitrogen content, high specific surface area, and porous characteristics. Our results can encourage the synthesis of high-performance carbon-based ORR electrocatalysts derived from widely-existed natural biomass.

The symbiotic relationship between dominant canopy trees and soil microbes affects the nitrogen source utilization of co-existing understory trees

Science.gov (United States)

Iwaoka, C.; Hyodo, F.; Taniguchi, T.; Shi, W.; Du, S.; Yamanaka, N.; Tateno, R.

2017-12-01

The symbiotic relationship between dominant canopy trees and soil microbes such as mycorrhiza or nitrogen (N) fixer are important determinants of soil N dynamics of a forest. However, it is not known how and to what extent the symbiotic relationship of dominant canopy trees with soil microbes affect the N source of co-existing trees in forest. We measured the δ15N of surface soils (0-10 cm), leaves, and roots of the dominant canopy trees and common understory trees in an arbuscular mycorrhizal N-fixing black locust (Robinia pseudoacacia) plantation and an ectomycorrhizal oak (Quercus liaotungensis) natural forest in a China dryland. We also analyzed the soil dissolved N content in soil extracts and absorbed by ion exchange resin, and soil ammonia-oxidizer abundance using real-time PCR. The δ15N of soil and leaves were higher in the black locust forest than in the oak forest, although the δ15N of fine roots was similar in the two forests, in co-existing understory trees as well as dominant canopy trees. Accordingly, the δ15N of leaves was similar to or higher than that of fine roots in the black locust forest, whereas it was consistently lower than that of fine roots in the oak forest. In the black locust forest, the soil dissolved organic N and ammonium N contents were less abundant but the nitrate N contents in soils and absorbed by the ion exchange resin and ammonia-oxidizer abundance were greater, due to N fixation or less uptake of organic N from arbuscular mycorrhiza. In contrast, the soil dissolved organic N and ammonium N contents were more abundant in the oak forest, whereas the N content featured very low nitrate, due to ectomycorrhizal ability to access organic N. These results suggest that the main N source is nitrate N in the black locust forest, but dissolved organic N or ammonium N in the oak forest. N fixation or high N loss due to high N availability would cause high δ15N in soil and leaves in black locust forest. On the other hand, low soil N

Carbon sequestration and Jerusalem artichoke biomass under nitrogen applications in coastal saline zone in the northern region of Jiangsu, China.

Science.gov (United States)

Niu, Li; Manxia, Chen; Xiumei, Gao; Xiaohua, Long; Hongbo, Shao; Zhaopu, Liu; Zed, Rengel

2016-10-15

Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in guream(-2)): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419gCkg(-1). Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0-10cm than 10-20cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied. Copyright © 2016 Elsevier B.V. All rights reserved.

Novel nitrogen-doped hierarchically porous coralloid carbon materials as host matrixes for lithium–sulfur batteries

International Nuclear Information System (INIS)

Yang, Jing; Wang, Shuyuan; Ma, Zhipeng; Du, Zhiling; Li, Chunying; Song, Jianjun; Wang, Guiling; Shao, Guangjie

2015-01-01

Highlights: • Nitrogen-doped hierarchically porous coralloid carbon/sulfur composites were prepared • Nitrogen atoms were introduced to improve electrochemical properties • The intriguing structural features benefited discharge capacity and cycling stability - Abstract: Nitrogen-doped hierarchically porous coralloid carbon/sulfur composites (N-HPCC/S) served as attractive cathode materials for lithium–sulfur (Li–S) batteries were fabricated for the first time. The nitrogen-doped hierarchically porous coralloid carbon (N-HPCC) with an appropriate nitrogen content (1.29 wt%) was synthesized via a facile hydrothermal approach, combined with subsequent carbonization–activation. The N-HPCC/S composites prepared by a simple melt–diffusion method displayed an excellent electrochemical performance. With a high sulfur content (58 wt%) in the total electrode weight, the N-HPCC/S cathode delivered a high initial discharge capacity of 1626.8 mA h g −1 and remained high up to 1086.3 mA h g −1 after 50 cycles at 100 mA g −1 , which is about 1.86 times as that of activated carbon. Particularly, the reversible discharge capacity still maintained 607.2 mA h g −1 after 200 cycles even at a higher rate of 800 mA g −1 . The enhanced electrochemical performance was attributed to the synergetic effect between the intriguing hierarchically porous coralloid structure and appropriate nitrogen doping, which could effectively trap polysulfides, alleviate the volume expansion, enhance the electronic conductivity and improve the surface interaction between the carbon matrix and polysulfides

Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil

KAUST Repository

Keuskamp, Joost A.

2013-02-01

Mangrove forests are sites of intense carbon and nutrient cycling, which result in soil carbon sequestration on a global scale. Currently, mangrove forests receive increasing quantities of exogenous nutrients due to coastal development. The present paper quantifies the effects of nutrient loading on microbial growth rates and the mineralisation of soil organic carbon (SOC) in two mangrove soils contrasting in carbon content. An increase in SOC mineralisation rates would lead to the loss of historically sequestered carbon and an enhanced CO2 release from these mangrove soils.In an incubation experiment we enriched soils from Avicennia and Rhizophora mangrove forests bordering the Red Sea with different combinations of nitrogen, phosphorus and glucose to mimic the effects of wastewater influx. We measured microbial growth rates as well as carbon mineralisation rates in the natural situation and after enrichment. The results show that microbial growth is energy limited in both soils, with nitrogen as a secondary limitation. Nitrogen amendment increased the rate at which labile organic carbon was decomposed, while it decreased SOC mineralisation rates. Such an inhibitory effect on SOC mineralisation was not found for phosphorus enrichment.Our data confirm the negative effect of nitrogen enrichment on the mineralisation of recalcitrant carbon compounds found in other systems. Based on our results it is not to be expected that nutrient enrichment by itself will cause degradation of historically sequestered soil organic carbon in nitrogen limited mangrove forests. © 2012 Elsevier Ltd.

Water- and plant-mediated responses of ecosystem carbon fluxes to warming and nitrogen addition on the Songnen grassland in northeast China.

Directory of Open Access Journals (Sweden)

Li Jiang

Full Text Available Understanding how grasslands are affected by a long-term increase in temperature is crucial to predict the future impact of global climate change on terrestrial ecosystems. Additionally, it is not clear how the effects of global warming on grassland productivity are going to be altered by increased N deposition and N addition.In-situ canopy CO(2 exchange rates were measured in a meadow steppe subjected to 4-year warming and nitrogen addition treatments. Warming treatment reduced net ecosystem CO(2 exchange (NEE and increased ecosystem respiration (ER; but had no significant impacts on gross ecosystem productivity (GEP. N addition increased NEE, ER and GEP. However, there were no significant interactions between N addition and warming. The variation of NEE during the four experimental years was correlated with soil water content, particularly during early spring, suggesting that water availability is a primary driver of carbon fluxes in the studied semi-arid grassland.Ecosystem carbon fluxes in grassland ecosystems are sensitive to warming and N addition. In the studied water-limited grassland, both warming and N addition influence ecosystem carbon fluxes by affecting water availability, which is the primary driver in many arid and semiarid ecosystems. It remains unknown to what extent the long-term N addition would affect the turn-over of soil organic matter and the C sink size of this grassland.

Canopy soil bacterial communities altered by severing host tree limbs

Directory of Open Access Journals (Sweden)

Cody R. Dangerfield

2017-09-01

Full Text Available Trees of temperate rainforests host a large biomass of epiphytic plants, which are associated with soils formed in the forest canopy. Falling of epiphytic material results in the transfer of carbon and nutrients from the canopy to the forest floor. This study provides the first characterization of bacterial communities in canopy soils enabled by high-depth environmental sequencing of 16S rRNA genes. Canopy soil included many of the same major taxonomic groups of Bacteria that are also found in ground soil, but canopy bacterial communities were lower in diversity and contained different operational taxonomic units. A field experiment was conducted with epiphytic material from six Acer macrophyllum trees in Olympic National Park, Washington, USA to document changes in the bacterial communities of soils associated with epiphytic material that falls to the forest floor. Bacterial diversity and composition of canopy soil was highly similar, but not identical, to adjacent ground soil two years after transfer to the forest floor, indicating that canopy bacteria are almost, but not completely, replaced by ground soil bacteria. Furthermore, soil associated with epiphytic material on branches that were severed from the host tree and suspended in the canopy contained altered bacterial communities that were distinct from those in canopy material moved to the forest floor. Therefore, the unique nature of canopy soil bacteria is determined in part by the host tree and not only by the physical environmental conditions associated with the canopy. Connection to the living tree appears to be a key feature of the canopy habitat. These results represent an initial survey of bacterial diversity of the canopy and provide a foundation upon which future studies can more fully investigate the ecological and evolutionary dynamics of these communities.

Dendrite-free Li metal anode enabled by a 3D free-standing lithiophilic nitrogen-enriched carbon sponge

Science.gov (United States)

Hou, Guangmei; Ren, Xiaohua; Ma, Xiaoxin; Zhang, Le; Zhai, Wei; Ai, Qing; Xu, Xiaoyan; Zhang, Lin; Si, Pengchao; Feng, Jinkui; Ding, Fei; Ci, Lijie

2018-05-01

Lithium metal is considered as the ultimate anode material for high-energy Li battery systems. However, the commercial application of lithium anode is impeded by issues with safety and low coulombic efficiency induced by Li dendrite growth. Herein, a free-standing three-dimensional nitrogen-enriched graphitic carbon sponge with a high nitrogen content is proposed as a multifunctional current collect for Lithium accommodation. The abundant lithiophilic N-containing functional groups are served as preferred nucleation sites to guide a uniform Li deposition. In addition, the nitrogen-enriched graphitic carbon sponge with a high specific surface area can effectively reduce the local current density. As a result of the synergistic effect, the nitrogen-enriched graphitic carbon sponge electrode realizes a long-term stable cycling without dendrites formation. Notably, the as-obtained composite electrode can deliver an ultra-high specific capacity of ∼3175 mA h g-1. The nitrogen-enriched graphitic carbon sponge might provide innovative insights to design a superior matrix for dendrite-free Li anode.

Relationships between NDVI, canopy structure, and photosynthesis in three California vegetation types

International Nuclear Information System (INIS)

Gamon, J.A.; Field, C.B.; Goulden, M.L.; Griffin, K.L.; Hartley, A.E.; Joel, G.; Penuelas, J.; Valentini, R.

1995-01-01

In a range of plant species from three Californian vegetation types, we examined the widely used ''normalized difference vegetation index'' (NDVI) and ''simple ratio'' (SR) as indicators of canopy structure, light absorption, and photosynthetic activity. These indices, which are derived from canopy reflectance in the red and near-infrared wavebands, highlighted phenological differences between evergreen and deciduous canopies. They were poor indicators of total canopy biomass due to the varying abundance of non-green standing biomass in these vegetation types. However, in sparse canopies (leaf area index (LAI) apprxeq 0-2), NDVI was a sensitive indicator of canopy structure and chemical content (green biomass, green leaf area index, chlorophyll content, and foliar nitrogen content). At higher canopy green LAI values ( gt 2; typical of dense shrubs and trees), NDVI was relatively insensitive to changes in canopy structure. Compared to SR, NDVI was better correlated with indicators of canopy structure and chemical content, but was equivalent to the logarithm of SR. In agreement with theoretical expectations, both NDVI and SR exhibited near-linear correlations with fractional PAR intercepted by green leaves over a wide range of canopy densities. Maximum daily photosynthetic rates were positively correlated with NDVI and SR in annual grassland and semideciduous shrubs where canopy development and photosynthetic activity were in synchrony. The indices were also correlated with peak springtime canopy photosynthetic rates in evergreens. However, over most of the year, these indices were poor predictors of photosynthetic performance in evergreen species due to seasonal reductions in photosynthetic radiation-use efficiency that occurred without substantial declines in canopy greenness. Our results support the use of these vegetation indices as remote indicators of PAR absorption, and thus potential photosynthetic activity, even in

Canopy position affects photosynthetic adjustments to long-term elevated CO{sub 2} concentration (FACE) in aging needles in a mature Pinus taeda forest

Energy Technology Data Exchange (ETDEWEB)

Crous, K. Y.; Ellsworth, D. S. [University of Michigan, School of Natural Resources and Environment, Ann Arbor, MI (United States)

2004-09-01

Results of an assessment of the long-term effects of exposure to elevated carbon dioxide in free-air enrichment (FACE) on two age classes of pine needles in the upper and lower canopy of a pine forest in North Carolina are discussed. The observations were made during the second through sixth year of exposure. A significant response was observed in 60 per cent of all age classes and canopy locations. Evidence of concurrent down-regulation of Rubisco and electron transport capacity in upper canopy sunlit leaves was noted beyond the sixth year. No such effect was seen in the lower canopy. Carboxylation capacity and electron transport capacity in the upper canopy was down-regulated by 17-20 per cent in one year-old needles, but this was significant across sampling years only for electron transport capacity. It is suggested that a reduction in photosynthetic capacity in aging conifer needles at the canopy top may have significant consequences for canopy carbon balance and global carbon sinks because a major proportion of the annual carbon balance of these conifers is contributed by one-year old sunlit needles. 45 refs., 3 tabs., 4 figs.

Spectroscopic study of nitrogen distribution in N-doped carbon nanotubes and nanofibers synthesized by catalytic ethylene-ammonia decomposition

Science.gov (United States)

Svintsitskiy, Dmitry A.; Kibis, Lidiya S.; Smirnov, Dmitry A.; Suboch, Arina N.; Stonkus, Olga A.; Podyacheva, Olga Yu.; Boronin, Andrei I.; Ismagilov, Zinfer R.

2018-03-01

Carbon and nitrogen species on the surface of carbon nanotubes (N-CNTs) and nanofibers (N-CNFs) were studied by X-ray absorption (XAS) and photoelectron spectroscopy (PES) including the analysis of nitrogen distribution over the depth of materials. The study was performed with a series of bamboo-like carbon nanotubes and nanofibers having the platelet-like and herringbone-like morphology. It was shown that the main nitrogen species in the composition of the studied materials are pyridine, pyrrole (and/or amino groups), graphite-like and oxidized states of nitrogen. In distinction to nanofibers, the bamboo-like nanotubes additionally contain molecular nitrogen encapsulated in the internal hollows. Spectral data for different depths of analysis were obtained by varying the energy of incident radiation. Such an approach revealed that N-CNTs are characterized by non-uniform distribution of chemically bound nitrogen species. Thus, nitrogen enrichment was observed on the external surface and in the internal arches of carbon nanotubes. Nitrogen enrichment in the subsurface region was found for N-CNFs, whereas the full depth analysis of N-distribution was limited by a large diameter of nanofibers.

Nitrogen in highly crystalline carbon nanotubes

International Nuclear Information System (INIS)

Ducati, C; Koziol, K; Stavrinadis, A; Friedrichs, S; Windle, A H; Midgley, P A

2006-01-01

Multiwall carbon nanotubes (MWCNTs) with an unprecedented degree of internal order were synthesised by chemical vapour deposition (CVD) adding a nitrogen-containing compound to the hydrocarbon feedstock. Ferrocene was used as the metal catalyst precursor. The remarkable crystallinity of these nanotubes lies both in the isochirality and in the crystallographic register of their walls, as demonstrated by electron diffraction and high resolution electron microscopy experiments. High resolution transmission electron microscopy analysis shows that the walls of the nanotubes consist of truncated stacked cones, instead of perfect cylinders, with a range of apex angles that appears to be related to the nitrogen concentration in the synthesis process. The structure of armchair, zigzag and chiral nanotubes is modelled and discussed in terms of density of topological defects, providing an interesting comparison with our microscopy experiments. A growth mechanism based on the interplay of base- and tip-growth is proposed to account for our experimental observations

Nitrogen reduction pathways in estuarine sediments: Influences of organic carbon and sulfide

Science.gov (United States)

Plummer, Patrick; Tobias, Craig; Cady, David

2015-10-01

Potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped across the entire Niantic River Estuary, CT, USA, at 100-200 m scale resolution consisting of 60 stations. On the estuary scale, denitrification accounted for ~ 90% of the nitrogen reduction, followed by DNRA and anammox. However, the relative importance of these reactions to each other was not evenly distributed through the estuary. A Nitrogen Retention Index (NIRI) was calculated from the rate data (DNRA/(denitrification + anammox)) as a metric to assess the relative amounts of reactive nitrogen being recycled versus retained in the sediments following reduction. The distribution of rates and accompanying sediment geochemical analytes suggested variable controls on specific reactions, and on the NIRI, depending on position in the estuary and that these controls were linked to organic carbon abundance, organic carbon source, and pore water sulfide concentration. The relationship between NIRI and organic carbon abundance was dependent on organic carbon source. Sulfide proved the single best predictor of NIRI, accounting for 44% of its observed variance throughout the whole estuary. We suggest that as a single metric, sulfide may have utility as a proxy for gauging the distribution of denitrification, anammox, and DNRA.

Spectroscopic properties of nitrogen doped hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition

International Nuclear Information System (INIS)

Hayashi, Y.; Yu, G.; Rahman, M. M.; Krishna, K. M.; Soga, T.; Jimbo, T.; Umeno, M.

2001-01-01

Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH 4 as the source of carbon and with different nitrogen flow rates (N 2 /CH 4 gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, electron spin resonance (ESR), photoluminescence (PL) and spectroscopic ellipsometry (SE). Raman spectroscopy and IR absorption reveal an increase in sp 2 -bonded carbon or a change in sp 2 domain size with increasing nitrogen flow rate. It is found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changes from nitrogen atoms surrounded by three (σ bonded) to two (π bonded) neighboring carbons with increasing nitrogen flow rate. Tauc optical gap is reduced from 2.6 to 2.0 eV, and the ESR spin density and the peak-to-peak linewidth increase sharply with increasing nitrogen flow rate. Excellent agreement has been found between the measured SE data and modeled spectra, in which an empirical dielectric function of amorphous materials and a linear void distribution along the thickness have been assumed. The influence of nitrogen on the electronic density of states is explained based on the optical properties measured by UV-VIS and PL including nitrogen lone pair band. [copyright] 2001 American Institute of Physics

Soil carbon and nitrogen mineralization under different tillage systems and Permanent Groundcover cultivation between Orange trees

Directory of Open Access Journals (Sweden)

Elcio Liborio Balota

2011-06-01

Full Text Available The objective of this work was to evaluate the alterations in carbon and nitrogen mineralization due to different soil tillage systems and groundcover species for intercropped orange trees. The experiment was established in an Ultisol soil (Typic Paleudults originated from Caiuá sandstone in northwestern of the state of Paraná, Brazil, in an area previously cultivated with pasture (Brachiaria humidicola. Two soil tillage systems were evaluated: conventional tillage (CT in the entire area and strip tillage (ST with a 2-m width, each with different groundcover vegetation management systems. The citrus cultivar utilized was the 'Pera' orange (Citrus sinensis grafted onto a 'Rangpur' lime rootstock. The soil samples were collected at a 0-15-cm depth after five years of experiment development. Samples were collected from under the tree canopy and from the inter-row space after the following treatments: (1 CT and annual cover crop with the leguminous Calopogonium mucunoides; (2 CT and perennial cover crop with the leguminous peanut Arachis pintoi; (3 CT and evergreen cover crop with Bahiagrass Paspalum notatum; (4 CT and cover crop with spontaneous B. humidicola grass vegetation; and (5 ST and maintenance of the remaining grass (pasture of B. humidicola. The soil tillage systems and different groundcover vegetation influenced the C and N mineralization, both under the tree canopy and in the inter-row space. The cultivation of B. humidicola under strip tillage provided higher potential mineralization than the other treatments in the inter-row space. Strip tillage increased the C and N mineralization compared to conventional tillage. The grass cultivation increased the C and N mineralization when compared to the others treatments cultivated in the inter-row space.

Nitrogen-Doped Carbon for Red Phosphorous Based Anode Materials for Lithium Ion Batteries

Directory of Open Access Journals (Sweden)

Jiaoyang Li

2018-01-01

Full Text Available Serving as conductive matrix and stress buffer, the carbon matrix plays a pivotal role in enabling red phosphorus to be a promising anode material for high capacity lithium ion batteries and sodium ion batteries. In this paper, nitrogen-doping is proved to effective enhance the interface interaction between carbon and red phosphorus. In detail, the adsorption energy between phosphorus atoms and oxygen-containing functional groups on the carbon is significantly reduced by nitrogen doping, as verified by X-ray photoelectron spectroscopy. The adsorption mechanisms are further revealed on the basis of DFT (the first density functional theory calculations. The RPNC (red phosphorus/nitrogen-doped carbon composite material shows higher cycling stability and higher capacity than that of RPC (red phosphorus/carbon composite anode. After 100 cycles, the RPNC still keeps discharge capacity of 1453 mAh g−1 at the current density of 300 mA g−1 (the discharge capacity of RPC after 100 cycles is 1348 mAh g−1. Even at 1200 mA g−1, the RPNC composite still delivers a capacity of 1178 mAh g−1. This work provides insight information about the interface interactions between composite materials, as well as new technology develops high performance phosphorus based anode materials.

Nitrogen-doped carbon nanotubes as a metal catalyst support

CSIR Research Space (South Africa)

Mabena, LF

2011-05-01

Full Text Available ., which are among the most commonly used heterogeneous catalyst supports (Mart??nez-Me?ndez et al. 2006). Catalyst activity depends on the particle size and appropriate dis- tance between each particle. These catalysts deposited on a support... supported Pt electrodes. Appl Catal B Environ 80:286?295 Maldonado S, Morin S, Stevenson KJ (2006) Structure, composition, and chemical reactivity of carbon nanotubes by selective nitrogen doping. Carbon 44:1429?1437 Mart??nez-Me?ndez S, Henr??quez Y...

Carbon and nitrogen - The key to biological activity, diversity and productivity in a Haplic Acrisol

International Nuclear Information System (INIS)

Okae-Anti, Daniel; Torkpo, Addison; Kankam-Boadu, Maryross; Agyei Frimpong, Kwame; Obuobi, Daniel

2004-10-01

Soil organic matter is important because it impacts all soil quality functions. Much less information is available on the dynamics of the residual carbon and nitrogen content and their distribution in continuously cropped arable fields. We described the values of the soil properties, pH, moisture content, organic carbon and total nitrogen considering them to be random variables. We treated their spatial variation as a function of the distance between observations within the study site, a continuously-cropped field dominated by Haplic Acrisols. We discussed the nature and structure of the modeled functions, the semivariograms, and interpreted these in the light of the potential of these soils to sustain agricultural productivity. At these sites there had been no conversion of natural forests to agriculture so the paper does not discuss soil carbon storage for either the regional or global storage. All the properties studied showed spatial non-stationarity for the distances covered, indicating that the variance between pairs of observations increased as separating distances also increased. pH, moisture content and total nitrogen were fitted with the power model whereas the linear model best fitted organic carbon. Total nitrogen had the least nugget variance and pH the highest estimated exponent, α, from the power equations. The soils are highly variable in terms of input or return of organic residue to provide a sink for carbon and nitrogen and the breakdown of these materials as affected by pH, moisture availability and microorganisms. (author)

Carbon and nitrogen - The key to biological activity, diversity and productivity in a Haplic Acrisol

Energy Technology Data Exchange (ETDEWEB)

Okae-Anti, Daniel [Department of Soil Science, School of Agriculture, University of Cape Coast, Cape Coast (Ghana); [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)] E-mail: dokaent@yahoo.co.uk; Torkpo, Addison; Kankam-Boadu, Maryross; Agyei Frimpong, Kwame [Department of Soil Science, School of Agriculture, University of Cape Coast, Cape Coast (Ghana); Obuobi, Daniel [Department of Computer Science and Information Technology, University of Cape Coast, Cape Coast (Ghana)

2004-10-01

Soil organic matter is important because it impacts all soil quality functions. Much less information is available on the dynamics of the residual carbon and nitrogen content and their distribution in continuously cropped arable fields. We described the values of the soil properties, pH, moisture content, organic carbon and total nitrogen considering them to be random variables. We treated their spatial variation as a function of the distance between observations within the study site, a continuously-cropped field dominated by Haplic Acrisols. We discussed the nature and structure of the modeled functions, the semivariograms, and interpreted these in the light of the potential of these soils to sustain agricultural productivity. At these sites there had been no conversion of natural forests to agriculture so the paper does not discuss soil carbon storage for either the regional or global storage. All the properties studied showed spatial non-stationarity for the distances covered, indicating that the variance between pairs of observations increased as separating distances also increased. pH, moisture content and total nitrogen were fitted with the power model whereas the linear model best fitted organic carbon. Total nitrogen had the least nugget variance and pH the highest estimated exponent, {alpha}, from the power equations. The soils are highly variable in terms of input or return of organic residue to provide a sink for carbon and nitrogen and the breakdown of these materials as affected by pH, moisture availability and microorganisms. (author)

Evaluation of the soil organic carbon, nitrogen and available ...

African Journals Online (AJOL)

The result obtained indicates that the level of these chemical properties were generally low as compared to standard measures and parameter for ratings soil fertility in the Nigerian Savanna. Keywords: Status of organic carbon, total nitrogen, available phosphorus, top horizons, research farm. Bowen Journal of Agriculture ...

Nitrogen, carbon, and sulfur metabolism in natural Thioploca samples

DEFF Research Database (Denmark)

Otte, S.; Kuenen, JG; Nielsen, LP

1999-01-01

Filamentous sulfur bacteria of the genus Thioploca occur as dense mats on the continental shelf off the coast of Chile and Peru. Since little is known about their nitrogen, sulfur, and carbon metabolism, this study was undertaken to investigate their (eco)physiology. Thioploca is able to store...

Kinetics and mechanisms of interactions of nitrogen and carbon monoxide with liquid niobium

International Nuclear Information System (INIS)

Park, H.G.

1990-01-01

The kinetics and mechanisms of interactions of N 2 and CO with liquid niobium were investigated in the temperature range of 2,700 to 3,000 K in samples levitated in N 2 /Ar and CO/Ar streams. The nitrogen absorption and desorption processes were found to be second-order with respect to nitrogen concentration, indicating that the rate controlling step is either the adsorption of nitrogen molecules on the liquid surface or dissociation of absorbed nitrogen molecules into adsorbed atoms. The carbon and oxygen dissolution in liquid niobium from CO gas is an exothermic process and the solubilities of carbon and oxygen (C Ce , C Oe in at%) are related to the temperature and the partial pressure of CO. The reaction CO → [C] + [O] along with the evaporation of niobium oxide takes place during C and O dissolution, whereas C and O desorption occurs via CO evolution only

Mutagenic effects of nitrogen and carbon ions on stevia

International Nuclear Information System (INIS)

Wang Cailian; Chen Qiufang; Shen Mei; Lu Ting; Shu Shizhen

1998-06-01

Dry seeds of stevia were implanted by 60∼100 keV nitrogen ion and 75 keV carbon ion with various doses. The biological effects in M 1 and mutation in M 2 were studied. The results showed that ion beam was able to induce variation on chromosome structure and inhibited mitosis action in root tip cells. The rate of cells with chromosome aberration was increased with the increase of ion beam energy and dose. Energy effects of mitosis were presented between 75 keV and 60, 100 keV. As compared with γ-rays, the effects of ion beam were lower on chromosomal aberration but were higher on frequency of the mutation. The rate of cell with chromosome aberration and M 2 useful mutation induced by implantation of carbon ion was higher than those induced by implantation of nitrogen ion. Mutagenic effects of Feng 1 x Ri Yuan and of Ri Yuan x Feng 2 are higher than that of Ji Ning and Feng 2

Comparing carbon to carbon: Organic and inorganic carbon balances across nitrogen fertilization gradients in rainfed vs. irrigated Midwest US cropland

Science.gov (United States)

Hamilton, S. K.; McGill, B.

2017-12-01

The top meter of the earth's soil contains about twice the amount of carbon than the atmosphere. Agricultural management practices influence whether a cropland soil is a net carbon source or sink. These practices affect both organic and inorganic carbon cycling although the vast majority of studies examine the former. We will present results from several rarely-compared carbon fluxes: carbon dioxide emissions and sequestration from lime (calcium carbonate) weathering, dissolved gases emitted from groundwater-fed irrigation, dissolved organic carbon (DOC) leaching to groundwater, and soil organic matter storage. These were compared in a corn-soybean-wheat rotation under no-till management across a nitrogen fertilizer gradient where half of the replicated blocks are irrigated with groundwater. DOC and liming fluxes are also estimated from a complementary study in neighboring plots comparing a gradient of management practices from conventional to biologically-based annuals and perennials. These studies were conducted at the Kellogg Biological Station Long Term Ecological Research site in Michigan where previous work estimated that carbon dioxide emissions from liming accounted for about one quarter of the total global warming impact (GWI) from no-till systems—our work refines that figure. We will present a first time look at the GWI of gases dissolved in groundwater that are emitted when the water equilibrates with the atmosphere. We will explore whether nitrogen fertilizer and irrigation increase soil organic carbon sequestration by producing greater crop biomass and residues or if they enhance microbial activity, increasing decomposition of organic matter. These results are critical for more accurately estimating how intensive agricultural practices affect the carbon balance of cropping systems.

Biogeochemical reactive transport of carbon, nitrogen and iron in the hyporheic zone

Science.gov (United States)

Dwivedi, D.; Steefel, C. I.; Newcomer, M. E.; Arora, B.; Spycher, N.; Hammond, G. E.; Moulton, J. D.; Fox, P. M.; Nico, P. S.; Williams, K. H.; Dafflon, B.; Carroll, R. W. H.

2017-12-01

To understand how biogeochemical processes in the hyporheic zone influence carbon and nitrogen cycling as well as stream biogeochemistry, we developed a biotic and abiotic reaction network and integrated it into a reactive transport simulator - PFLOTRAN. Three-dimensional reactive flow and transport simulations were performed to describe the hyporheic exchange of fluxes from and within an intra-meander region encompassing two meanders of East River in the East Taylor watershed, Colorado. The objectives of this study were to quantify (1) the effect of transience on the export of carbon, nitrogen, and iron; and (2) the biogeochemical transformation of nitrogen and carbon species as a function of the residence time. The model was able to capture reasonably well the observed trends of nitrate and dissolved oxygen values that decreased as well as iron (Fe (II)) values that increased along the meander centerline away from the stream. Hyporheic flow paths create lateral redox zonation within intra-meander regions, which considerably impact nitrogen export into the stream system. Simulation results further demonstrated that low water conditions lead to higher levels of dissolved iron in groundwater, which (Fe (II)> 80%) is exported to the stream on the downstream side during high water conditions. An important conclusion from this study is that reactive transport models representing spatial and temporal heterogeneities are required to identify important factors that contribute to the redox gradients at riverine scales.

Exploring Relationships between Canopy Architecture, Light Distribution, and Photosynthesis in Contrasting Rice Genotypes Using 3D Canopy Reconstruction

Directory of Open Access Journals (Sweden)

Alexandra J. Burgess

2017-05-01

Full Text Available The arrangement of leaf material is critical in determining the light environment, and subsequently the photosynthetic productivity of complex crop canopies. However, links between specific canopy architectural traits and photosynthetic productivity across a wide genetic background are poorly understood for field grown crops. The architecture of five genetically diverse rice varieties—four parental founders of a multi-parent advanced generation intercross (MAGIC population plus a high yielding Philippine variety (IR64—was captured at two different growth stages using a method for digital plant reconstruction based on stereocameras. Ray tracing was employed to explore the effects of canopy architecture on the resulting light environment in high-resolution, whilst gas exchange measurements were combined with an empirical model of photosynthesis to calculate an estimated carbon gain and total light interception. To further test the impact of different dynamic light patterns on photosynthetic properties, an empirical model of photosynthetic acclimation was employed to predict the optimal light-saturated photosynthesis rate (Pmax throughout canopy depth, hypothesizing that light is the sole determinant of productivity in these conditions. First, we show that a plant type with steeper leaf angles allows more efficient penetration of light into lower canopy layers and this, in turn, leads to a greater photosynthetic potential. Second the predicted optimal Pmax responds in a manner that is consistent with fractional interception and leaf area index across this germplasm. However, measured Pmax, especially in lower layers, was consistently higher than the optimal Pmax indicating factors other than light determine photosynthesis profiles. Lastly, varieties with more upright architecture exhibit higher maximum quantum yield of photosynthesis indicating a canopy-level impact on photosynthetic efficiency.

[Characteristics of 'salt island' and 'fertile island' for Tamarix chinensis and soil carbon, nitrogen and phosphorus ecological stoichiometry in saline-alkali land].

Science.gov (United States)

Zhang, Li-hua; Chen, Xiao-bing

2015-03-01

To clarify the nutrient characteristics of 'salt island' and 'fertile island' effects in saline-alkali soil, the native Tamarix chinensis of the Yellow River Delta (YRD) was selected to measure its soil pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (N), total phosphorus (P) and their stoichiometry characteristics at different soil depths. The results showed that soil pH and EC increased with the increasing soil depth. Soil EC and P in the 0-20 cm layer decreased and increased from canopied area to interspace, respectively. SOC, N, N/P and C/P in the 20-40 cm soil layer decreased, and C/N increased from the shrub center to interspace. SOC and N contents between island and interspace both decreased but P content decreased firstly and then increased with the increasing soil depth. Soil pH correlated positively with EC. In addition, pH and EC correlated negatively with C, N, P contents and their ecological stoichiometry.

Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests.

Science.gov (United States)

Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

2014-08-01

Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2 ) and tropospheric ozone (O3 ) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3 . Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r(2) = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m(-2) ) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (∆NPP/∆N) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2 . Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. © 2014 The Authors Global Change Biology Published by John Wiley & Sons Ltd.

Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests

Science.gov (United States)

Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

2014-01-01

Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3. Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r2 = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m−2) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (ΔNPP/ΔN) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2. Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

Fast Conversion of Ionic Liquids and Poly(Ionic Liquid)s into Porous Nitrogen-Doped Carbons in Air.

Science.gov (United States)

Men, Yongjun; Ambrogi, Martina; Han, Baohang; Yuan, Jiayin

2016-04-08

Ionic liquids and poly(ionic liquid)s have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m²/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection.

Missing Peroxy Radical Sources Within a Rural Forest Canopy

Science.gov (United States)

Wolfe, G. M.; Cantrell, C.; Kim, S.; Mauldin, R. L., III; Karl, T.; Harley, P.; Turnipseed, A.; Zheng, W.; Flocke, F.; Apel, E. C.;

Effects of canopy light distribution characteristics and leaf nitrogen content on efficiency of radiation use in dry matter accumulation of soybean [Glycine max] cultivars

International Nuclear Information System (INIS)

Shiraiwa, T.; Hashikawa, U.; Taka, S.; Sakai, A.

1994-01-01

The amount of dry matter produced per photosynthetically active radiation (PAR) intercepted by the canopy (EPAR) and factors which might affect EPAR were determined for various soybean cultivars, and their relationships were also analyzed in two field experiments. In 1989 and 1990, 11 cultivars and 27 cultivars respectively, were grown on an experimental field in shiga Prefectural Junior College. Changes of intercepted PAR, top dry matter weight, light extinction coefficient (KPAR), nitrogen content per leaf area (SLN) and nitrogen accumulation in the top (1990 only) were measured. EPAR averaged for all the cultivars was 2.48g MJ(-1) in both years and its coefficient of variance among cultivars was +- 9% in 1989 and +- 17% in 1990. In general, recent cultivars showed greater EPAR than older ones. The correlation coefficients between SLN and EPAR were 0.548 in 1989 and 0.651-- in 1990, while there was no correlation between KPAR and EPAR. Since SLN showed close correlation with SLW (r = 0.954 in 1989, r = 0.170-- in 1990), the difference in EPAR between old and new cultivars was considered to be attributable mainly to the improved leaf morphological trait and consequently greater leaf photosynthesis of newer cultivars. SLN further correlated with total top nitrogen content (r = 0.736-- in 1990) thus seemed to be limited by nitrogen accumulation

Preparation of nitrogen-doped graphene/activated carbon composite papers to enhance energy storage in supercapacitors

Science.gov (United States)

Li, Yong-feng; Liu, Yan-zhen; Liang, Yu; Guo, Xiao-hui; Chen, Cheng-meng

2017-09-01

This report presents a facile and effective method to synthesize freestanding nitrogen-doped reduced graphene oxide (rGO)/activated carbon (AC) composite papers for supercapacitors by a method combining vacuum filtration with post-annealing in NH3 atmosphere. The effect of activated carbon contents on the microstructure and capacitive behavior of the resulting composite papers before and after the annealing was investigated by X-ray diffraction, scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy. Results show that the composite paper with a 30% activated carbon loading has a high nitrogen content of 14.6 at% and superior capacitive performance (308 F/g, 1 A/g) to the other composite papers with various activated carbon loadings. Nitrogen was doped and GO reduced during the annealing. The rGO nanosheets acted as a framework, and the AC particles served as spacers to avoid agglomeration of graphene sheets. The high capacitance of the composite paper is ascribed to the electric double-layer behavior and the reversible redox reactions of the nitrogen and oxygen groups. The entire process is simple, environmental friendly and easily scalable for mass production.

Effect of canopy architectural variation on transpiration and thermoregulation

Science.gov (United States)

Linn, R.; Banerjee, T.

2017-12-01

One of the major scientific questions identified by the NGEE - Tropics campaign is the effect of disturbances such as forest fires, vegetation thinning and land use change on carbon, water and energy fluxes. Answers to such questions can help develop effective forest management strategies and shape policies to mitigate damages under natural and anthropogenic climate change. The absence of horizontal and vertical variation of forest canopy structure in current models is a major source of uncertainty in answering these questions. The current work addresses this issue through a bottom up process based modeling approach to systematically investigate the effect of forest canopy architectural variation on plant physiological response as well as canopy level fluxes. A plant biophysics formulation is used which is based on the following principles: (1) a model for the biochemical demand for CO2 as prescribed by photosynthesis models. This model can differentiate between photosynthesis under light-limited and nutrient-limited scenarios. (2) A Fickian mass transfer model including transfer through the laminar boundary layer on leaves that may be subjected to forced or free convection depending upon the mean velocity and the radiation load; (3) an optimal leaf water use strategy that maximizes net carbon gain for a given transpiration rate to describe the stomatal aperture variation; (4) a leaf-level energy balance to accommodate evaporative cooling. Such leaf level processes are coupled to solutions of atmospheric flow through vegetation canopies. In the first test case, different scenarios of top heavy and bottom heavy (vertical) foliage distributions are investigated within a one-dimensional framework where no horizontal heterogeneity of canopy structure is considered. In another test case, different spatial distributions (both horizontal and vertical) of canopy geometry (land use) are considered, where flow solutions using large eddy simulations (LES) are coupled to the

Regulation of Carbon Flow by Nitrogen and Light in the Red Alga, Gelidium coulteri1

Science.gov (United States)

Macler, Bruce A.

1986-01-01

The red alga Gelidium coulteri Harv. photosynthetically fixed [14C] bicarbonate at high rates under defined conditions in unialgal laboratory culture. The fixation rate and flow of photosynthate into various end products were dependent on the nitrogen status of the tissue. Plants fed luxury levels of nitrogen (approximately 340 micromolar) showed fixation rates several-fold higher than those seen for plants starved for nitrogen. The addition of NO3− or NH4+ to such starved plants further inhibited fixation over at least the first several hours after addition. The majority of 14C after incubations of 30 minutes to 8 hours was found in the compounds floridoside, agar and floridean starch. In addition, amino acids and intermediate compounds of the reductive pentose phosphate pathway, glycolytic pathway and tricarboxylic acid cycle were detected. Nitrogen affected the partitioning of labeled carbon into these compounds. Plants under luxury nitrogen conditions had higher floridoside levels and markedly lower amounts of agar and starch than found in plants limited for nitrogen. Amino acid, phycobiliprotein and chlorophyll levels were also significantly higher in nitrogen-enriched plants. Addition of NO3− to starved plants led to an increase in floridoside, tricarboxylic acid cycle intermediates and amino acids within 1 hour and inhibited carbon flow into agar and starch. Carbon fixation in the dark was only 1 to 7% of that seen in the light. Dark fixation of [14C]bicarbonate yielded label primarily in tricarboxylic acid cycle intermediates, amino acids and polysaccharides. Nitrogen stimulated amino acid synthesis at the expense of agar and starch. Floridoside was only a minor component in the dark. Pulse-chase experiments, designed to show carbon turnover, indicated a 2-fold increase in labeling of agar over 96 hours of chase in the light. No increases were seen in the dark. Low molecular weight pools, including floridoside, decreased 2- to 5-fold over this period

Carbon Dioxide and Nitrogen Infused Compressed Air Foam for Depopulation of Caged Laying Hens

Science.gov (United States)

Gurung, Shailesh; White, Dima; Archer, Gregory; Styles, Darrel; Zhao, Dan; Farnell, Yuhua; Byrd, James; Farnell, Morgan

2018-01-01

Simple Summary Compressed air, detergent, and water make up compressed air foam. Our laboratory has previously reported that compressed air foam may be an effective method for mass depopulation of caged layer hens. Gases, such as carbon dioxide and nitrogen, have also been used for poultry euthanasia and depopulation. The objective of this study was to produce compressed air foam infused with carbon dioxide or nitrogen to compare its efficacy against foam with air and gas inhalation methods (carbon dioxide or nitrogen) for depopulation of caged laying hens. The study showed that a carbon dioxide-air mixture or 100% nitrogen can replace air to make compressed air foam. However, the foam with carbon dioxide had poor foam quality compared to the foam with air or nitrogen. The physiological stress response of hens subjected to foam treatments with and without gas infusion did not differ significantly. Hens exposed to foam with nitrogen died earlier as compared to methods such as foam with air and carbon dioxide. The authors conclude that infusion of nitrogen into compressed air foam results in better foam quality and shortened time to death as compared to the addition of carbon dioxide. Abstract Depopulation of infected poultry flocks is a key strategy to control and contain reportable diseases. Water-based foam, carbon dioxide inhalation, and ventilation shutdown are depopulation methods available to the poultry industry. Unfortunately, these methods have limited usage in caged layer hen operations. Personnel safety and welfare of birds are equally important factors to consider during emergency depopulation procedures. We have previously reported that compressed air foam (CAF) is an alternative method for depopulation of caged layer hens. We hypothesized that infusion of gases, such as carbon dioxide (CO2) and nitrogen (N2), into the CAF would reduce physiological stress and shorten time to cessation of movement. The study had six treatments, namely a negative control

Chemical bonding modifications of tetrahedral amorphous carbon and nitrogenated tetrahedral amorphous carbon films induced by rapid thermal annealing

International Nuclear Information System (INIS)

McCann, R.; Roy, S.S.; Papakonstantinou, P.; Bain, M.F.; Gamble, H.S.; McLaughlin, J.A.

2005-01-01

Tetrahedral amorphous carbon (ta-C) and nitrogenated tetrahedral amorphous carbon films (ta-CN x ), deposited by double bend off plane Filtered Vacuum Cathodic Arc were annealed up to 1000 deg. C in flowing argon for 2 min. Modifications on the chemical bonding structure of the rapidly annealed films, as a function of temperature, were investigated by NEXAFS, X-ray photoelectron and Raman spectroscopies. The interpretation of these spectra is discussed. The results demonstrate that the structure of undoped ta-C films prepared at floating potential with an arc current of 80 A remains stable up to 900 deg. C, whereas that of ta-CN x containing 12 at.% nitrogen is stable up to 700 deg. C. At higher temperatures, all the spectra indicated the predominant formation of graphitic carbon. Through NEXAFS studies, we clearly observed three π* resonance peaks at the ' N K edge structure. The origin of these three peaks is not well established in the literature. However our temperature-dependant study ascertained that the first peak originates from C=N bonds and the third peak originates from the incorporation of nitrogen into the graphite like domains

Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

Directory of Open Access Journals (Sweden)

Yang Wang

2014-01-01

Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

Synthesis of nitrogen doped microporous carbons prepared by activation-free method and their high electrochemical performance

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Seok [Department of Chemistry, Inha University, Incheon 402-751 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, Incheon 402-751 (Korea, Republic of)

2011-11-30

Graphical abstract: This describes the increase of specific capacitance in hybrid electrodes as a function of melamine content. Display Omitted Highlights: > For N-enriched hybrid carbons, co-precursors, PVDF/melamine composites, were used. > Microporous carbons were formed by only carbonization without chemical activation. > The nitrogen content of microporous carbons was controlled by melamine content. > N-doped carbons showed higher specific capacitance compared to microporous carbons. > It was attributed to the easy electron transfer and pseudocapacitance. - Abstract: Nitrogen-doped microporous carbons (N-MCs) were prepared by the carbonization of the polyvinylidene fluoride (PVDF)/melamine mixture without chemical activation. The electrochemical performance of the N-MCs was investigated as a function of PVDF/melamine ratio. It was found that, without additional activation, the N-MCs had a high specific surface area (greater than 560 m{sup 2}/g) because of the micropore formation by the release of fluorine groups. In addition, although the specific surface area decreased, nitrogen groups were increased with increasing melamine content, leading to an enhanced electrochemical performance. Indeed, the N-MCs showed a better electrochemical performance than that of microporous carbons (MCs) prepared by PVDF alone, and the highest specific capacitance (310 F/g) was obtained at a current density of 0.5 A/g, as compared to a value of 248 F/g for MCs. These results indicate that the microporous features of N-MC lead to feasible ion transfer during charge/discharge duration and the presence of nitrogen groups as strong electron donor on the N-MC electrode in electrolyte could provide a pseudocapacitance by the redox reaction.

Oxygen- and nitrogen-co-doped activated carbon from waste particleboard for potential application in high-performance capacitance

International Nuclear Information System (INIS)

Shang, Tong-Xin; Ren, Ru-Quan; Zhu, Yue-Mei; Jin, Xiao-Juan

2015-01-01

Graphical abstract: All electrodes showed excellent capacitance and retention versus discharge current density from 0.05 to 5 A/g. - Abstract: Oxygen- and nitrogen-co-doped activated carbons were obtained from phosphoric acid treated nitrogen-doped activated carbons which were prepared from waste particleboard bonded with urea-formaldehyde resin adhesives. The activated carbon samples obtained were tested as supercapacitors in two-electrode cell and extensive wetting 7 M KOH electrolytes. Their structural properties and surface chemistry, before the electrical testing, were investigated using elemental analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction, Raman spectra, and adsorption of nitrogen. Activated carbon treated by 4 M phosphoric acid of the highest capacitance (235 F/g) was measured in spite of a relatively lower surface (1360 m 2 /g) than that of the activated carbon treated by 2 M phosphoric acid (1433 m 2 /g). The surface chemistry, and especially oxygen- and nitrogen-containing functional groups, was found of paramount importance for the capacitive behavior and for the effective pore space utilization by the electrolyte ions

Available nitrogen: A time-based study of manipulated resource islands

Science.gov (United States)

Stubbs, Michelle M.; Pyke, David A.

2005-01-01

Spatial and temporal heterogeneity of available nitrogen are critical determinants of the distribution and abundance of plants and animals in ecosystems. Evidence for the resource island theory suggests that soils below tree and shrub canopies contain higher amounts of resources, including available nitrogen, than are present in interspace areas. Disturbances, such as prescribed fire and tree removal, are common management practices in shrub-woodland ecosystems, but it is not known if these practices affect resource islands. We examined temporal variation in resource islands of available nitrogen and their retention after fire and woody plant removal. From August 1997 to October 1998, soil nitrate (NO3−) and ammonium (NH4+) were measured monthly from canopy and interspace plots within four juniper-sagebrush sites along a precipitation gradient in central Oregon, USA. At each site, soil samples were collected from untreated plots, plots in which woody plants were removed, and those treated with prescribed fire in fall 1997. In burned treatments, canopy concentrations were significantly higher than interspace concentrations throughout the measurement period. Canopy NO3− and NH4+ concentrations were significantly higher on burned vs. unburned treatments for four months after fire. After woody plant removal, NO3− and NH4+ concentrations did not differ from the controls. Untreated control areas had higher NO3− and NH4+ concentrations under juniper canopies for nearly all months. Wetter sites had smaller differences between canopy and interspace concentrations through time than did the two drier sites. In relation to NO3− and NH4+ in this ecosystem, resource islands appear to be more ephemeral in wetter sites, and more pronounced following fire disturbances than in controls or those treated by woody plant removal.

Nitrogen doped activated carbon from pea skin for high performance supercapacitor

Science.gov (United States)

Ahmed, Sultan; Ahmed, Ahsan; Rafat, M.

2018-04-01

In this work, nitrogen doped porous carbon (NDC) has been synthesized employing a facile two-step process. Firstly, carbon precursor (pea skin) was heated with melamine (acting as nitrogen source) followed by activation with KOH in different ratios. The dependence of porosity and nitrogen content on impregnation ratio was extensively studied. Other textural properties of prepared NDC sample were studied using standard techniques of material characterization. The electrochemical performance of NDC sample as an electrode was studied in two-electrode symmetric supercapacitor system. 1 M LiTFSI (lithium bis-trifluoromethanesulfonimide) solution in IL EMITFSI (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), was used as electrolyte. It was found that the fabricated supercapacitor cell offers high values of specific capacitance (141.1 F g‑1), specific energy (19.6 Wh kg‑1) and specific power (25.4 kW kg‑1) at current density of 1.3 A g‑1. More importantly, the fabricated supercapacitor cell shows capacitance retention of ∼75%, for more than 5000 cycles. The enhanced performance of NDC sample is primarily due to large surface area with favorable surface structure (contributing to double layer capacitance) and presence of nitrogen functionalities (contributing to pseudo-capacitance). Such important features make the synthesized NDC sample, an attractive choice for electrode material in high performance supercapacitor.

Revealing the Origin of Activity in Nitrogen-Doped Nanocarbons towards Electrocatalytic Reduction of Carbon Dioxide

DEFF Research Database (Denmark)

Xu, Junyuan; Kan, Yuhe; Huang, Rui

2016-01-01

Carbon nanotubes (CNTs) are functionalized with nitrogen atoms for reduction of carbon dioxide (CO2). The investigation explores the origin of the catalyst’s activity and the role of nitrogen chemical states therein. The catalysts show excellent performances, with about 90% current efficiency...... for CO formation and stability over 60 hours. The Tafel analyses and density functional theory calculations suggest that the reduction of CO2 proceeds through an initial rate-determining transfer of one electron to CO2, which leads to the formation of carbon dioxide radical anion (CO2C). The initial...

[Effects of carbon and nitrogen sources on 5-keto-gluconic acid production].

Science.gov (United States)

Tan, Zhilei; Wang, Hongcui; Wei, Yuqiao; Li, Yanyan; Zhong, Cheng; Jia, Shiru

2014-01-01

Gluconobacter oxydans is known to oxidize glucose to gluconic acid (GA), and subsequently, to 2-keto-gluconic acid (2KGA) and 5-keto-gluconic acid (5KGA), while 5KGA can be converted to L-(+)-tartaric acid. In order to increase the production of 5KGA, Gluconobacter oxydans HGI-1 that converts GA to 5KGA exclusively was chosen in this study, and effects of carbon sources (lactose, maltose, sucrose, amylum and glucose) and nitrogen sources (yeast extract, fish meal, corn steep liquor, soybean meal and cotton-seed meal) on 5KGA production were investigated. Results of experiment in 500 mL shake-flask show that the highest yield of 5KGA (98.20 g/L) was obtained using 100 g/L glucose as carbon source. 5KGA reached 100.20 g/L, 109.10 g/L, 99.83 g/L with yeast extract, fish meal and corn steep liquor as nitrogen source respectively, among which the optimal nitrogen source was fish meal. The yield of 5KGA by corn steep liquor is slightly lower than that by yeast extract. For the economic reason, corn steep liquor was selected as nitrogen source and scaled up to 5 L stirred-tank fermentor, and the final concentration of 5KGA reached 93.80 g/L, with its maximum volumetric productivity of 3.48 g/(L x h) and average volumetric productivity of 1.56 g/(L x h). The result obtained in this study showed that carbon and nitrogen sourses for large-scale production of 5KGA by Gluconobacter oxydans HGI-1 were glucose and corn steep liquor, respectively, and the available glucose almost completely (85.93%) into 5KGA.

Modeling of carbon and nitrogen gaseous emissions from cattle manure compost windrows

Science.gov (United States)

Windrow composting of cattle manure is a significant source of gaseous emissions, which include ammonia (NH3) and the greenhouse gases (GHGs) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). A manure compost model was developed to simulate carbon (C) and nitrogen (N) processes includ...

The Crc protein inhibits the production of polyhydroxyalkanoates in Pseudomonas putida under balanced carbon/nitrogen growth conditions.

Science.gov (United States)

La Rosa, Ruggero; de la Peña, Fernando; Prieto, María Axiliadora; Rojo, Fernando

2014-01-01

Pseudomonas putida synthesizes polyhydroxyalkanoates (PHAs) as storage compounds. PHA synthesis is more active when the carbon source is in excess and the nitrogen source is limiting, but can also occur at a lower rate under balanced carbon/nitrogen ratios. This work shows that PHA synthesis is controlled by the Crc global regulator, a protein that optimizes carbon metabolism by inhibiting the expression of genes involved in the use of non-preferred carbon sources. Crc acts post-transcriptionally. The mRNAs of target genes contain characteristic catabolite activity (CA) motifs near the ribosome binding site. Sequences resembling CA motifs can be predicted for the phaC1 gene, which codes for a PHA polymerase, and for phaI and phaF, which encode proteins associated to PHA granules. Our results show that Crc inhibits the translation of phaC1 mRNA, but not that of phaI or phaF, reducing the amount of PHA accumulated in the cell. Crc inhibited PHA synthesis during exponential growth in media containing a balanced carbon/nitrogen ratio. No inhibition was seen when the carbon/nitrogen ratio was imbalanced. This extends the role of Crc beyond that of controlling the hierarchical utilization of carbon sources and provides a link between PHA synthesis and the global regulatory networks controlling carbon flow. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

Minerilization of carbon and nitrogen of organic residues from ...

African Journals Online (AJOL)

Minerilization of carbon and nitrogen of organic residues from selected plants in a tropical cropping system. O M Onuh, HA Okorie. Abstract. No Abstract. Journal of Agriculture and Food Sciences Vol. 3 (1) 2005 pp. 11-24. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Episodic Canopy Structural Transformations and Biological Invasion in a Hawaiian Forest

Directory of Open Access Journals (Sweden)

Christopher S. Balzotti

2017-07-01

Full Text Available The remaining native forests on the Hawaiian Islands have been recognized as threatened by changing climate, increasing insect outbreak, new deadly pathogens, and growing populations of canopy structure-altering invasive species. The objective of this study was to assess long-term, net changes to upper canopy structure in sub-montane forests on the eastern slope of Mauna Kea volcano, Hawai‘i, in the context of continuing climate events, insect outbreaks, and biological invasion. We used high-resolution multi-temporal Light Detection and Ranging (LiDAR data to quantify near-decadal net changes in forest canopy height and gap distributions at a critical transition between alien invaded lowland and native sub-montane forest at the end of a recent drought and host-specific insect (Scotorythra paludicola outbreak. We found that sub-montane forests have experienced a net loss in average canopy height, and therefore structure and aboveground carbon stock. Additionally, where invasive alien tree species co-dominate with native trees, the upper canopy structure became more homogeneous. Tracking the loss of forest canopy height and spatial variation with airborne LiDAR is a cost-effective way to monitor forest canopy health, and to track and quantify ecological impacts of invasive species through space and time.

Metal-Organic-Framework-Mediated Nitrogen-Doped Carbon for CO2 Electrochemical Reduction

KAUST Repository

Wang, Riming; Sun, Xiaohui; Ould-Chikh, Samy; Osadchii, Dmitrii; Bai, Fan; Kapteijn, Freek; Gascon, Jorge

2018-01-01

A nitrogen-doped carbon was synthesized through the pyrolysis of the well-known metal-organic framework ZIF-8, followed by a subsequent acid treatment, and has been applied as a catalyst in the electrochemical reduction of carbon dioxide. The resulting electrode shows Faradaic efficiencies to carbon monoxide as high as ∼78%, with hydrogen being the only byproduct. The pyrolysis temperature determines the amount and the accessibility of N species in the carbon electrode, in which pyridinic-N and quaternary-N species play key roles in the selective formation of carbon monoxide.

Metal-Organic-Framework-Mediated Nitrogen-Doped Carbon for CO2 Electrochemical Reduction

KAUST Repository

Wang, Riming

2018-04-11

A nitrogen-doped carbon was synthesized through the pyrolysis of the well-known metal-organic framework ZIF-8, followed by a subsequent acid treatment, and has been applied as a catalyst in the electrochemical reduction of carbon dioxide. The resulting electrode shows Faradaic efficiencies to carbon monoxide as high as ∼78%, with hydrogen being the only byproduct. The pyrolysis temperature determines the amount and the accessibility of N species in the carbon electrode, in which pyridinic-N and quaternary-N species play key roles in the selective formation of carbon monoxide.

Structural investigation of two carbon nitride solids produced by cathodic arc deposition and nitrogen implantation

Energy Technology Data Exchange (ETDEWEB)

Merchant, A R; McCulloch, D; McKenzie, D R; Yin, Y; Gerstner, E G [New South Wales Univ., Kensington, NSW (Australia)

1997-12-31

Carbon nitride materials have been the focus of research efforts worldwide. Most materials studied have been amorphous, with only a few groups claiming to have found a crystalline material. In this paper, carbon nitride materials prepared by two different techniques are analysed, and found to be remarkably similar in bonding and structure. The materials appear to have a primarily sp{sup 2} bonded carbon structure with a lower bond length than found in an amorphous carbon. This is explained by nitrogen substituting into `rings` to a saturation level of about one nitrogen per three carbon atoms. No evidence was found for a crystalline structure of formula C{sub 3}N{sub 4}, or any amorphous derivative of it. 16 refs., 1 tab., 5 figs.

Structural investigation of two carbon nitride solids produced by cathodic arc deposition and nitrogen implantation

Energy Technology Data Exchange (ETDEWEB)

Merchant, A.R.; McCulloch, D.; McKenzie, D.R.; Yin, Y.; Gerstner, E.G. [New South Wales Univ., Kensington, NSW (Australia)

1996-12-31

Carbon nitride materials have been the focus of research efforts worldwide. Most materials studied have been amorphous, with only a few groups claiming to have found a crystalline material. In this paper, carbon nitride materials prepared by two different techniques are analysed, and found to be remarkably similar in bonding and structure. The materials appear to have a primarily sp{sup 2} bonded carbon structure with a lower bond length than found in an amorphous carbon. This is explained by nitrogen substituting into `rings` to a saturation level of about one nitrogen per three carbon atoms. No evidence was found for a crystalline structure of formula C{sub 3}N{sub 4}, or any amorphous derivative of it. 16 refs., 1 tab., 5 figs.

Structural investigation of two carbon nitride solids produced by cathodic arc deposition and nitrogen implantation

International Nuclear Information System (INIS)

Merchant, A.R.; McCulloch, D.; McKenzie, D.R.; Yin, Y.; Gerstner, E.G.

1996-01-01

Carbon nitride materials have been the focus of research efforts worldwide. Most materials studied have been amorphous, with only a few groups claiming to have found a crystalline material. In this paper, carbon nitride materials prepared by two different techniques are analysed, and found to be remarkably similar in bonding and structure. The materials appear to have a primarily sp 2 bonded carbon structure with a lower bond length than found in an amorphous carbon. This is explained by nitrogen substituting into 'rings' to a saturation level of about one nitrogen per three carbon atoms. No evidence was found for a crystalline structure of formula C 3 N 4 , or any amorphous derivative of it. 16 refs., 1 tab., 5 figs

Statistical models for prediction of dry weight and nitrogen accumulation based on visible and near-infrared hyper-spectral reflectance of rice canopies

International Nuclear Information System (INIS)

Takahashi, W.; Nguyen-Cong, V.; Kawaguchi, S.; Minamiyama, M.; Ninomiya, S.

2000-01-01

Various multivariate regression models were examined with ten-fold cross-validation to develop efficient, accurate models to predict dry weight and nitrogen accumulation of rice crops (cultivars Koshihikari, Hanaechizen, Nipponbare, and IR-36) from the maximum tiller number stage to the meiosis stage, using plant-canopy reflectance of hyper-spectra within the 400-1100 nm domain without any variable selection. The results showed that the principal component regression using hyper-spectra gave better fits and predictability than that using specific wavelengths. On the other hand, partial least squares regression was the most useful among the models tested; this method avoided overfitting and multicollinearity by using all wavelength information without variable selection and by inclusion of both x and y variations in its latent variables. (author)

Boreal mire carbon exchange: sensitivity to climate change and anthropogenic nitrogen and sulfur deposition

Energy Technology Data Exchange (ETDEWEB)

Eriksson, Tobias

2010-07-01

Boreal peatlands are important long-term sinks of atmospheric carbon and in the same time the largest natural source of methane to the atmosphere. A changing climate as well as deposition of anthropogenically derived pollutants, such as nitrogen and sulfur, has the potential to affect the processes that control the carbon exchange in peatlands. Many of the biogeochemical responses to changed environmental conditions, such as changed plant community composition, are slow and therefore long-term studies are required. In this thesis I have investigated the long-term effects of nitrogen addition, sulfur addition and greenhouse enclosures on carbon exchange by using a field manipulation experiment in a boreal minerogenic, oligotrophic mire after 10-12 years of treatment. Treatment effects on CH{sub 4} emissions, gross primary production (GPP), ecosystem respiration (Reco) and net ecosystem exchange (NEE) were estimated from 1-2 seasons of chamber flux measurements. Treatment effects on potential CH{sub 4} production and oxidation were estimated in incubations of peat from different depth intervals. The effect of nitrogen deposition on carbon accumulation was evaluated in peat cores at different depth intervals. The long-term nitrogen additions have: shifted plant community composition from being dominated by Sphagnum to being dominated by sedges and dwarf shrubs; changed mire surface microtopography so that mean water table is closer to the surface in plots with high nitrogen; increased CH{sub 4} production and emission; increased Reco slightly but have not affected GPP or NEE; reduced the peat height increment, but increased both peat bulk density and carbon content, leading to an unchanged carbon accumulation. The long-term sulfur additions have not reduced CH{sub 4} emissions, only slightly reduced CH{sub 4} production and did not have any effect on the CO{sub 2} carbon exchange. The greenhouse treatment, manifested in increased air and soil temperatures, reduced

Synthesis of ultrathin nitrogen-doped graphitic carbon nanocages as advanced electrode materials for supercapacitor.

Science.gov (United States)

Tan, Yueming; Xu, Chaofa; Chen, Guangxu; Liu, Zhaohui; Ma, Ming; Xie, Qingji; Zheng, Nanfeng; Yao, Shouzhuo

2013-03-01

Synthesis of nitrogen-doped carbons with large surface area, high conductivity, and suitable pore size distribution is highly desirable for high-performance supercapacitor applications. Here, we report a novel protocol for template synthesis of ultrathin nitrogen-doped graphitic carbon nanocages (CNCs) derived from polyaniline (PANI) and their excellent capacitive properties. The synthesis of CNCs involves one-pot hydrothermal synthesis of Mn3O4@PANI core-shell nanoparticles, carbonization to produce carbon coated MnO nanoparticles, and then removal of the MnO cores by acidic treatment. The CNCs prepared at an optimum carbonization temperature of 800 °C (CNCs-800) have regular frameworks, moderate graphitization, high specific surface area, good mesoporosity, and appropriate N doping. The CNCs-800 show high specific capacitance (248 F g(-1) at 1.0 A g(-1)), excellent rate capability (88% and 76% capacitance retention at 10 and 100 A g(-1), respectively), and outstanding cycling stability (~95% capacitance retention after 5000 cycles) in 6 M KOH aqueous solution. The CNCs-800 can also exhibit great pseudocapacitance in 0.5 M H2SO4 aqueous solution besides the large electrochemical double-layer capacitance. The excellent capacitance performance coupled with the facile synthesis of ultrathin nitrogen-doped graphitic CNCs indicates their great application potential in supercapacitors.

Synthesis of nitrogen doped microporous carbons prepared by activation-free method and their high electrochemical performance

International Nuclear Information System (INIS)

Kim, Ki-Seok; Park, Soo-Jin

2011-01-01

Graphical abstract: This describes the increase of specific capacitance in hybrid electrodes as a function of melamine content. Display Omitted Highlights: → For N-enriched hybrid carbons, co-precursors, PVDF/melamine composites, were used. → Microporous carbons were formed by only carbonization without chemical activation. → The nitrogen content of microporous carbons was controlled by melamine content. → N-doped carbons showed higher specific capacitance compared to microporous carbons. → It was attributed to the easy electron transfer and pseudocapacitance. - Abstract: Nitrogen-doped microporous carbons (N-MCs) were prepared by the carbonization of the polyvinylidene fluoride (PVDF)/melamine mixture without chemical activation. The electrochemical performance of the N-MCs was investigated as a function of PVDF/melamine ratio. It was found that, without additional activation, the N-MCs had a high specific surface area (greater than 560 m 2 /g) because of the micropore formation by the release of fluorine groups. In addition, although the specific surface area decreased, nitrogen groups were increased with increasing melamine content, leading to an enhanced electrochemical performance. Indeed, the N-MCs showed a better electrochemical performance than that of microporous carbons (MCs) prepared by PVDF alone, and the highest specific capacitance (310 F/g) was obtained at a current density of 0.5 A/g, as compared to a value of 248 F/g for MCs. These results indicate that the microporous features of N-MC lead to feasible ion transfer during charge/discharge duration and the presence of nitrogen groups as strong electron donor on the N-MC electrode in electrolyte could provide a pseudocapacitance by the redox reaction.

Search for correlatable, isotopically light carbon and nitrogen components in Lunar soils and breccias

International Nuclear Information System (INIS)

Norris, S.J.; Swart, P.K.; Wright, I.P.; Grady, M.M.; Pillinger, C.T.

1983-01-01

Using stepped heating extraction techniques, determinations of carbon and nitrogen content and delta 13 C and delta 15 N values have been obtained for selected lunar soils and breccias. Only nitrogen data have been gathered for representative splits separated by size, density and magnetic properties from 12023. A plot of the total delta 13 C (after terrestrial contamination is removed) versus delta 15 N values for the bulk samples reveals little evidence for a correlation between isotopically light carbon and isotopically light nitrogen of putative ancient solar wind origin. Soil 12023 is used to examine the current interpretation for the stepped release profile of nitrogen from bulk lunar samples. Mature agglutinates, postulated by previous workers to be the host of the light nitrogen, are shown to have a very constant delta 15 N value which is heavy rather than light. The actual host of the light nitrogen in 12023 has not been identified. The lowest values encountered during the study were found associated with the finest soil, but none of these was as low as for some temperature steps of the bulk soil. Interpretations regarding the origin of light nitrogen, if it is not present in agglutinates, await the results of more definitive efforts to identify the host phase

Subtropical urban turfs: Carbon and nitrogen pools and the role of enzyme activity.

Science.gov (United States)

Kong, Ling; Chu, L M

2018-03-01

Urban grasslands not only provide a recreational venue for urban residents, but also sequester organic carbon in vegetation and soils through photosynthesis, and release carbon dioxide through respiration, which largely contribute to carbon storage and fluxes at regional and global scales. We investigated organic carbon and nitrogen pools in subtropical turfs and found that dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were regulated by several factors including microbial activity which is indicated by soil enzymatic activity. We observed a vertical variation and different temporal patterns in both soil DOC, DON and enzyme activities, which decreased significantly with increasing soil depths. We further found that concentration of soil DON was linked with turf age. There were correlations between grass biomass and soil properties, and soil enzyme activities. In particular, soil bulk density was significantly correlated with soil moisture and soil organic carbon (SOC). In addition, DOC correlated significantly with DON. Significant negative correlations were also observed between soil total dissolved nitrogen (TDN) and grass biomass of Axonopus compressus and Zoysia matrella. Specifically, grass biomass was significantly correlated with the soil activity of urease and β-glucosidase. Soil NO 3 -N concentration also showed negative correlations with the activity of both β-glucosidase and protease but there were no significant correlations between cellulase and soil properties or grass biomass. Our study demonstrated a relationship between soil C and N dynamics and soil enzymes that could be modulated to enhance SOC pools through management and maintenance practices. Copyright © 2017. Published by Elsevier B.V.

Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

International Nuclear Information System (INIS)

Zhao Peng; Zhang Ying; Wang Pei-Ji; Zhang Zhong; Liu De-Sheng

2011-01-01

Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C 60 nanotube caps. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Leaf Potential Productivity at Different Canopy Levels in Densely-planted and Intermediately-thinned Apple Orchards

Directory of Open Access Journals (Sweden)

Ying SUN

2016-07-01

Full Text Available Most apple orchards in the apple production districts in China were densely planted with vigorous rootstocks during the 1980s. These orchards have suffered micro-environmental deterioration and loss of fruit quality because of the closed canopy. Modification of the densely-planted orchards is a priority in current apple production. Intermediate thinning is a basic technique used to transform densely-planted apple orchards in China. Our goal was to provide theoretical basis for studying the effect of thinning on the efficiency of photosynthetically active radiation (PAR, fruit quality, and yield. We measured leaf area, solar radiation, and leaf air exchange at different tree canopy levels and by fitting relevant photosynthetic models, vertical distribution characteristics of leaf photosynthetic potentials and PAR were analyzed in various levels within canopies in densely-planted and intermediately-thinned orchards. Intermediate thinning significantly improved the radiant environment inside the canopies. PAR distribution within the canopies in the intermediately-thinned orchard was better distributed than in the densely-planted orchards. The invalid space under 30.0% of relative photosynthetically active radiation (PARr was nearly zero in the intermediately-thinned orchard; but minimum PARr was 17.0% and the space under 0.30 of the relative height of the canopy was invalid for photosynthesis in the densely-planted orchard. The leaf photosynthetic efficiency in the intermediately-thinned orchard was improved. Photosynthetic rates (Pn at the middle and bottom levels of the canopy, respectively, were increased by 7.80% and 10.20% in the intermediately-thinned orchard. Leaf development, which influences photosynthetic potential, was closely related to the surrounding micro-environment, especially light. Leaf photosynthetic potentials were correlated with leaf nitrogen content (Nl and specific leaf weight (Ml at various levels of canopies. Compared

Effects of nitrogen and carbon sources on the production of inulinase from strain Bacillus sp. SG113

Science.gov (United States)

Gavrailov, Simeon; Ivanova, Viara

2016-03-01

The effects of the carbon and nitrogen substrates on the growth of Bacillus sp. SG113 strain were studied. The use of organic nitrogen sources (peptone, beef extract, yeast extract, casein) leads to rapid cellular growth and the best results for the Bacillus strain were obtained with casein hydrolysate. From the inorganic nitrogen sources studied, the (NH4) 2SO4 proved to be the best nitrogen source. Casein hydrolysate and (NH4) 2SO4 stimulated the invertase synthesis. In the presence of Jerusalem artichoke, onion and garlic extracts as carbon sources the strain synthesized from 6 to 10 times more inulinase.

Nitrogen-modified carbon nanostructures derived from metal-organic frameworks as high performance anodes for Li-ion batteries

International Nuclear Information System (INIS)

Shen, Cai; Zhao, Chongchong; Xin, Fengxia; Cao, Can; Han, Wei-Qiang

2015-01-01

Here, we report preparation of nitrogen-modified nanostructure carbons through carbonization of Cu-based metal organic nanofibers at 700 °C under argon gas atmosphere. After removal of copper through chemical treatment with acids, pure N-modified nanostructure carbon with a nitrogen content of 8.62 wt% is obtained. When use as anodes for lithium-ion battery, the nanostructure carbon electrode has a discharge capacity of 853.1 mAh g −1 measured at a current of 500 mA g −1 after 800 cycles.

Investigation of the Influence of Leaf Thickness on Canopy Reflectance and Physiological Traits in Upland and Pima Cotton Populations

Directory of Open Access Journals (Sweden)

Duke Pauli

2017-08-01

Full Text Available Many systems for field-based, high-throughput phenotyping (FB-HTP quantify and characterize the reflected radiation from the crop canopy to derive phenotypes, as well as infer plant function and health status. However, given the technology's nascent status, it remains unknown how biophysical and physiological properties of the plant canopy impact downstream interpretation and application of canopy reflectance data. In that light, we assessed relationships between leaf thickness and several canopy-associated traits, including normalized difference vegetation index (NDVI, which was collected via active reflectance sensors carried on a mobile FB-HTP system, carbon isotope discrimination (CID, and chlorophyll content. To investigate the relationships among traits, two distinct cotton populations, an upland (Gossypium hirsutum L. recombinant inbred line (RIL population of 95 lines and a Pima (G. barbadense L. population composed of 25 diverse cultivars, were evaluated under contrasting irrigation regimes, water-limited (WL and well-watered (WW conditions, across 3 years. We detected four quantitative trait loci (QTL and significant variation in both populations for leaf thickness among genotypes as well as high estimates of broad-sense heritability (on average, above 0.7 for both populations, indicating a strong genetic basis for leaf thickness. Strong phenotypic correlations (maximum r = −0.73 were observed between leaf thickness and NDVI in the Pima population, but not the RIL population. Additionally, estimated genotypic correlations within the RIL population for leaf thickness with CID, chlorophyll content, and nitrogen discrimination (r^gij = −0.32, 0.48, and 0.40, respectively were all significant under WW but not WL conditions. Economically important fiber quality traits did not exhibit significant phenotypic or genotypic correlations with canopy traits. Overall, our results support considering variation in leaf thickness as a potential

Enhanced photosynthetic capacity increases nitrogen metabolism through the coordinated regulation of carbon and nitrogen assimilation in Arabidopsis thaliana.

Science.gov (United States)

Otori, Kumi; Tanabe, Noriaki; Maruyama, Toshiki; Sato, Shigeru; Yanagisawa, Shuichi; Tamoi, Masahiro; Shigeoka, Shigeru

2017-09-01

Plant growth and productivity depend on interactions between the metabolism of carbon and nitrogen. The sensing ability of internal carbon and nitrogen metabolites (the C/N balance) enables plants to regulate metabolism and development. In order to investigate the effects of an enhanced photosynthetic capacity on the metabolism of carbon and nitrogen in photosynthetically active tissus (source leaves), we herein generated transgenic Arabidopsis thaliana plants (ApFS) that expressed cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase in their chloroplasts. The phenotype of ApFS plants was indistinguishable from that of wild-type plants at the immature stage. However, as plants matured, the growth of ApFS plants was superior to that of wild-type plants. Starch levels were higher in ApFS plants than in wild-type plants at 2 and 5 weeks. Sucrose levels were also higher in ApFS plants than in wild-type plants, but only at 5 weeks. On the other hand, the contents of various free amino acids were lower in ApFS plants than in wild-type plants at 2 weeks, but were similar at 5 weeks. The total C/N ratio was the same in ApFS plants and wild-type plants, whereas nitrite levels increased in parallel with elevations in nitrate reductase activity at 5 weeks in ApFS plants. These results suggest that increases in the contents of photosynthetic intermediates at the early growth stage caused a temporary imbalance in the free-C/free-N ratio and, thus, the feedback inhibition of the expression of genes involved in the Calvin cycle and induction of the expression of those involved in nitrogen metabolism due to supply deficient free amino acids for maintenance of the C/N balance in source leaves of ApFS plants.

3D analysis of the morphology and spatial distribution of nitrogen in nitrogen-doped carbon nanotubes by energy-filtered transmission electron microscopy tomography.

Science.gov (United States)

Florea, Ileana; Ersen, Ovidiu; Arenal, Raul; Ihiawakrim, Dris; Messaoudi, Cédric; Chizari, Kambiz; Janowska, Izabela; Pham-Huu, Cuong

2012-06-13

We present here the application of the energy-filtered transmission electron microscopy (EFTEM) in the tomographic mode to determine the precise 3D distribution of nitrogen within nitrogen-doped carbon nanotubes (N-CNTs). Several tilt series of energy-filtered images were acquired on the K ionization edges of carbon and nitrogen on a multiwalled N-CNT containing a high amount of nitrogen. Two tilt series of carbon and nitrogen 2D maps were then calculated from the corresponding energy-filtered images by using a proper extraction procedure of the chemical signals. Applying iterative reconstruction algorithms provided two spatially correlated C and N elemental-selective volumes, which were then simultaneously analyzed with the shape-sensitive reconstruction deduced from Zero-Loss recordings. With respect to the previous findings, crucial information obtained by analyzing the 3D chemical maps was that, among the two different kind of arches formed in these nanotubes (transversal or rounded ones depending on their morphology), the transversal arches contain more nitrogen than do the round ones. In addition, a detailed analysis of the shape-sensitive volume allowed the observation of an unexpected change in morphology along the tube axis: close to the round arches (with less N), the tube is roughly cylindrical, whereas near the transversal ones (with more N), its shape changes to a prism. This relatively new technique is very powerful in the material science because it combines the ability of the classical electron tomography to solve 3D structures and the chemical selectivity of the EFTEM imaging.

CO{sub 2} removal potential of carbons prepared by co-pyrolysis of sugar and nitrogen containing compounds

Energy Technology Data Exchange (ETDEWEB)

Arenillas, A.; Drage, T.C.; Smith, K.; Snape, C.E. [University of Nottingham, Fuel Science Group, School of Chemical, Environmental and Mining Engineering, University Park, Nottingham NG7 2RD (United Kingdom)

2005-08-15

The nitrogen enrichment of active carbons is reported to be effective in enhancing the specific adsorbate-adsorbent interactions for CO{sub 2}. In this work, nitrogen-enriched carbons were prepared by co-pyrolysis of sugar and a series of nitrogen compounds with different nitrogen functionalities. The results show that although the amount of nitrogen incorporated to the final adsorbent is important, the N-functionality seems to be more relevant for increasing CO{sub 2} uptake. Thus, the adsorbent obtained from urea co-pyrolysis presents the highest nitrogen content but the lowest CO{sub 2} adsorption capacity. However, the adsorbent obtained from carbazole co-pyrolysis, despite the lower amount of N incorporated, shows high CO{sub 2} uptake, up to 9wt.%, probably because the presence of more basic functionalities as determined by XPS analysis.

Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations

Science.gov (United States)

Gregory P. Asner; Michael Palace; Michael Keller; Rodrigo Pereira Jr.; Jose N. M. Silva; Johan C. Zweede

2002-01-01

Canopy structural data can be used for biomass estimation and studies of carbon cycling, disturbance, energy balance, and hydrological processes in tropical forest ecosystems. Scarce information on canopy dimensions reflects the difficulties associated with measuring crown height, width, depth, and area in tall, humid tropical forests. New field and spaceborne...

Constraining the Exchange of Carbon and Nitrogen in Eastern Long Island Sound

Science.gov (United States)

Byrd, A.; Warren, J. K.; Vlahos, P.; Whitney, M. M.

2017-12-01

Long Island Sound (LIS) is an urban estuary on the US east coast that undergoes seasonal hypoxia in its western and central regions. Currently, the budgets of both carbon and nitrogen in LIS remain unbalanced, despite their importance to the efficient and strategic management of the health of coastal and aquatic ecosystems. In this study, we evaluated the exchange values of C and N at the mouth of LIS (the Race), in order to constrain export through this important boundary. Discreet water samples were collected during four 15 km transects over the Race at five stations and three depths each station to resolve the temporal variability over a complete tidal cycle, in order to assess both net flux and variations across the tidal period. By evaluating both the particulate and dissolved pools of carbon (POC, PIC, DOC, DIC) and nitrogen (PON, DON, DIN) during the spring, summer and winter (high and low flow conditions) and pairing these measurements with physical data, we were able to identify a variety of forcing and export regimes. Preliminary results indicate the importance of spatial and tidal variability on flux estimates and show little or no export (and sometimes import) of nitrogen and significant export of organic carbon.

Effects of nitrogen- and oxygen-containing functional groups of activated carbon nanotubes on the electrochemical performance in supercapacitors

Science.gov (United States)

Liu, Haiyan; Song, Huaihe; Chen, Xiaohong; Zhang, Su; Zhou, Jisheng; Ma, Zhaokun

2015-07-01

A kind of nitrogen- and oxygen-containing activated carbon nanotubes (ACNTs) has been prepared by carbonization and activation of polyaniline nanotubes obtained by rapidly mixed reaction. The ACNTs show oxygen content of 15.7% and nitrogen content of 2.97% (atomic ratio). The ACNTs perform high capacitance and good rate capability (327 F g-1 at the current density of 10 A g-1) when used as the electrode materials for supercapacitors. Hydrogen reduction has been further used to investigate the effects of surface functional groups on the electrochemical performance. The changes for both structural component and electrochemical performance reveal that the quinone oxygen, pyridinic nitrogen, and pyrrolic nitrogen of carbon have the most obvious influence on the capacitive property because of their pseudocapacitive contributions.

Structure, thermodynamic and electronic properties of carbon-nitrogen cubanes and protonated polynitrogen cations

Science.gov (United States)

Chaban, Vitaly V.; Andreeva, Nadezhda A.

2017-12-01

Energy generation and storage are at the center of modern civilization. Energetic materials constitute quite a large class of compounds with a high amount of stored chemical energy that can be released. We hereby use a combination of quantum chemistry methods to investigate feasibility and properties of carbon-nitrogen cubanes and multi-charged polynitrogen cations in the context of their synthesis and application as unprecedented energetic materials. We show that the stored energy increases gradually with the nitrogen content increase. Nitrogen-poor cubanes retain their stabilities in vacuum, even at elevated temperatures. Such molecules will be probably synthesized at some point. In turn, polynitrogen cations are highly unstable, except N8H+, despite they are isoelectronic to all-carbon cubane. Kinetic stability of the cation decays drastically as its total charge increases. High-level thermodynamic calculations revealed that large amounts of energy are liberated upon decompositions of polynitrogen cations, which produce molecular nitrogen, acetylene, and protons. The present results bring a substantial insights to the design of novel high-energy compounds.

Modelling nitrogen saturation and carbon accumulation in heathland soils under elevated nitrogen deposition

International Nuclear Information System (INIS)

Evans, C.D.; Caporn, S.J.M.; Carroll, J.A.; Pilkington, M.G.; Wilson, D.B.; Ray, N.; Cresswell, N.

2006-01-01

A simple model of nitrogen (N) saturation, based on an extension of the biogeochemical model MAGIC, has been tested at two long-running heathland N manipulation experiments. The model simulates N immobilisation as a function of organic soil C/N ratio, but permits a proportion of immobilised N to be accompanied by accumulation of soil carbon (C), slowing the rate of C/N ratio change and subsequent N saturation. The model successfully reproduced observed treatment effects on soil C and N, and inorganic N leaching, for both sites. At the C-rich upland site, N addition led to relatively small reductions in soil C/N, low inorganic N leaching, and a substantial increase in organic soil C. At the C-poor lowland site, soil C/N ratio decreases and N leaching increases were much more dramatic, and soil C accumulation predicted to be smaller. The study suggests that (i) a simple model can effectively simulate observed changes in soil and leachate N; (ii) previous model predictions based on a constant soil C pool may overpredict future N leaching; (iii) N saturation may develop most rapidly in dry, organic-poor, high-decomposition systems; and (iv) N deposition may lead to significantly enhanced soil C sequestration, particularly in wet, nutrient-poor, organic-rich systems. - Enhanced carbon sequestration may slow the rate of nitrogen saturation in heathlands

Modelling pollutant deposition to vegetation: scaling down from the canopy to the biochemical level

International Nuclear Information System (INIS)

Taylor, G.E. Jr.; Constable, J.V.H.

1994-01-01

In the atmosphere, pollutants exist in either the gas, particle or liquid (rain and cloud water) phase. The most important gas-phase pollutants from a biological or ecological perspective are oxides of nitrogen (nitrogen dioxide, nitric acid vapor), oxides of sulfur (sulfur dioxide), ammonia, tropospheric ozone and mercury vapor. For liquid or particle phase pollutants, the suite of pollutants is varied and includes hydrogen ion, multiple heavy metals, and select anions. For many of these pollutants, plant canopies are a major sink within continental landscapes, and deposition is highly dependent on the (i) physical form or phase of the pollutant, (ii) meteorological conditions above and within the plant canopy, and (iii) physiological or biochemical properties of the leaf, both on the leaf surface and within the leaf interior. In large measure, the physical and chemical processes controlling deposition at the meteorological and whole-canopy levels are well characterized and have been mathematically modelled. In contrast, the processes operating on the leaf surface and within the leaf interior are not well understood and are largely specific for individual pollutants. The availability of process-level models to estimate deposition is discussed briefly at the canopy and leaf level; however, the majority of effort is devoted to modelling deposition at the leaf surface and leaf interior using the two-layer stagnant film model. This model places a premium on information of a physiological and biochemical nature, and highlights the need to distinguish clearly between the measurements of atmospheric chemistry and the physiologically effective exposure since the two may be very dissimilar. A case study of deposition in the Los Angeles Basin is used to demonstrate the modelling approach, to present the concept of exposure dynamics in the atmosphere versus that in the leaf interior, and to document the principle that most forest canopies are exposed to multiple chemical

Effects of organic nitrogen and carbon sources on mycelial growth ...

African Journals Online (AJOL)

Grifola umbellate is a famous and expensive Chinese herb medicine and the main medicinal component is polysaccharide mainly produced by its mycelia. Effects of organic nitrogen and carbon resources on mycelial growth and polysaccharides production of a medicinal mushroom, G. umbellate were studied in the ...

Effects of carbon and nitrogen sources on the induction and ...

African Journals Online (AJOL)

user

about the induction and repression mechanism of this hydrolytic enzyme. This report ... chitin as a sole source of carbon followed by the medium containing an extra nitrogen source, yeast extract. .... against fluorescent background by UV illumination. Statistical ..... Virulence Associated with Native and Mutant Isolates of an.

Effects of carbon and nitrogen sources on the induction and ...

African Journals Online (AJOL)

Effects of carbon and nitrogen sources on the induction and repression of chitinase enzyme from Beauveria bassiana isolates. Priyanka Dhar, Gurvinder Kaur. Abstract. Beauveria bassiana a natural soil borne insect pathogen is being used effectively these days in integrated pest management system. Foliar application of ...

Nitrogen-Containing Functional Groups-Facilitated Acetone Adsorption by ZIF-8-Derived Porous Carbon

Directory of Open Access Journals (Sweden)

Liqing Li

2018-01-01

Full Text Available Nitrogen-doped porous carbon (ZC is prepared by modification with ammonia for increasing the specific surface area and surface polarity after carbonization of zeolite imidazole framework-8 (ZIF-8. The structure and properties of these ZCs were characterized by Transmission electron microscopy, X-ray diffraction, N2 sorption, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Through static adsorption tests of these carbons, the sample obtained at 600 °C was selected as an excellent adsorbent, which exhibited an excellent acetone capacity of 417.2 mg g−1 (25 °C with a very large surface area and high-level nitrogen doping (13.55%. The microporosity, surface area and N-containing groups of the materials, pyrrolic-N, pyridinic-N, and oxidized-N groups in particular, were found to be the determining factors for acetone adsorption by means of molecular simulation with density functional theory. These findings indicate that N-doped microporous carbon materials are potential promising adsorbents for acetone.

Hyperspectral data mining to identify relevant canopy spectral features for estimating durum wheat growth, nitrogen status, and yield

Science.gov (United States)

Modern hyperspectral sensors permit reflectance measurements of crop canopies in hundreds of narrow spectral wavebands. While these sensors describe plant canopy reflectance in greater detail than multispectral sensors, they also suffer from issues with data redundancy and spectral autocorrelation. ...

Reassessing carbon sequestration in the North China Plain via addition of nitrogen

Energy Technology Data Exchange (ETDEWEB)

Dong, Wenxu, E-mail: dongwx@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Duan, Yongmei, E-mail: 106086193@QQ.com [Geological Survey of Jiangxi Province, Nanchang 330030 (China); Wang, Yuying, E-mail: wangyy@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Hu, Chunsheng, E-mail: cshu@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China)

2016-09-01

Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage and dissolution at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0–100 cm depths and the concentration of dissolved inorganic carbon (DIC) in soil leachate in 4 N application treatments (0, 200, 400, and 600 kg N ha{sup −1} yr{sup −1}) for 15 years in the North China Plain. The objectives were to evaluate the effect of nitrogen fertilizer on total amount of carbon sequestration and the uptake of atmospheric CO{sub 2} in an agricultural system. Results showed that after 15 years of N fertilizer application the SOC contents at depths of 0–100 cm significantly increased, whereas the SIC contents significantly decreased at depths of 0–60 cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO{sub 3}{sup −} and the HCO{sub 3}{sup −} / (Ca{sup 2+} + Mg{sup 2+}) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0–80 cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO{sub 2} and less influenced by protons through the nitrification which would release CO{sub 2}. To accurately evaluate soil C sequestration under N input scenarios in semi-arid regions, future studies should include both changes in SIC storage as well as the fractions of dissolution with different sources of acids in soil profiles. - Highlights: • The SOC contents significantly increased after long-term nitrogen application, while SIC decreased. • The measured loss of carbonate was far higher than the theoretical values of dissolution from

A microbial biogeochemistry network for soil carbon and nitrogen cycling and methane flux: model structure and application to Asia

Science.gov (United States)

Xu, X.; Song, C.; Wang, Y.; Ricciuto, D. M.; Lipson, D.; Shi, X.; Zona, D.; Song, X.; Yuan, F.; Oechel, W. C.; Thornton, P. E.

2017-12-01

A microbial model is introduced for simulating microbial mechanisms controlling soil carbon and nitrogen biogeochemical cycling and methane fluxes. The model is built within the CN (carbon-nitrogen) framework of Community Land Model 4.5, named as CLM-Microbe to emphasize its explicit representation of microbial mechanisms to biogeochemistry. Based on the CLM4.5, three new pools were added: bacteria, fungi, and dissolved organic matter. It has 11 pools and 34 transitional processes, compared with 8 pools and 9 transitional flow in the CLM4.5. The dissolve organic carbon was linked with a new microbial functional group based methane module to explicitly simulate methane production, oxidation, transport and their microbial controls. Comparing with CLM4.5-CN, the CLM-Microbe model has a number of new features, (1) microbial control on carbon and nitrogen flows between soil carbon/nitrogen pools; (2) an implicit representation of microbial community structure as bacteria and fungi; (3) a microbial functional-group based methane module. The model sensitivity analysis suggests the importance of microbial carbon allocation parameters on soil biogeochemistry and microbial controls on methane dynamics. Preliminary simulations validate the model's capability for simulating carbon and nitrogen dynamics and methane at a number of sites across the globe. The regional application to Asia has verified the model in simulating microbial mechanisms in controlling methane dynamics at multiple scales.

Improving representation of nitrogen uptake, allocation, and carbon assimilation in the Community Land Model

Science.gov (United States)

Ghimire, B.; Riley, W. J.; Koven, C.

2013-12-01

Nitrogen is the most important nutrient limiting plant carbon assimilation and growth, and is required for production of photosynthetic enzymes, growth and maintenance respiration, and maintaining cell structure. The forecasted rise in plant available nitrogen through atmospheric nitrogen deposition and the release of locked soil nitrogen by permafrost thaw in high latitude ecosystems is likely to result in an increase in plant productivity. However a mechanistic representation of plant nitrogen dynamics is lacking in earth system models. Most earth system models ignore the dynamic nature of plant nutrient uptake and allocation, and further lack tight coupling of below- and above-ground processes. In these models, the increase in nitrogen uptake does not translate to a corresponding increase in photosynthesis parameters, such as maximum Rubisco capacity and electron transfer rate. We present an improved modeling framework implemented in the Community Land Model version 4.5 (CLM4.5) for dynamic plant nutrient uptake, and allocation to different plant parts, including leaf enzymes. This modeling framework relies on imposing a more realistic flexible carbon to nitrogen stoichiometric ratio for different plant parts. The model mechanistically responds to plant nitrogen uptake and leaf allocation though changes in photosynthesis parameters. We produce global simulations, and examine the impacts of the improved nitrogen cycling. The improved model is evaluated against multiple observations including TRY database of global plant traits, nitrogen fertilization observations and 15N tracer studies. Global simulations with this new version of CLM4.5 showed better agreement with the observations than the default CLM4.5-CN model, and captured the underlying mechanisms associated with plant nitrogen cycle.

Nitrogen removal from coal gasification wastewater by activated carbon technologies combined with short-cut nitrogen removal process.

Science.gov (United States)

Zhao, Qian; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng; Jia, Shengyong; Fang, Fang

2014-11-01

A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal (GAC-PACT-SBNR) was developed to enhance total nitrogen (TN) removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%-49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAC compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand (COD) degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater (CGW). Copyright © 2014. Published by Elsevier B.V.

Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

Science.gov (United States)

Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

2015-04-01

Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

Mesoporous nitrogen-doped carbon microfibers derived from Mg-biquinoline-dicarboxy compound for efficient oxygen electroreduction

Energy Technology Data Exchange (ETDEWEB)

Kong, Aiguo, E-mail: agkong@chem.ecnu.edu.cn [School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241 (China); Fan, Xiaohong; Chen, Aoling [School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241 (China); Zhang, Hengiang [School of Chemistry and Chemical Engineering, Hebei Normal University for Nationalities, Chengde 067000 (China); Shan, Yongkui, E-mail: agkong@chem.ecnu.edu.cn [School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241 (China)

2017-02-15

An in-situ MgO-templating synthesis route was introduced to obtain the mesoporous nitrogen-doped carbon microfibers by thermal conversion of new Mg-2,2′-biquinoline 4,4-dicarboxy acid coordination compound (Mg-DCA) microfibers. The investigated crystal structure of Mg-DCA testified that the assembling of Mg{sup 2+} and DCA through Mg-O coordination bond and hydrogen bond contributed to the formation of one-dimensional (1D) crystalline Mg-DCA microfibers. The nitrogen-doped carbons derived from the pyrolysis of Mg-DCA showed the well-defined microfiber morphology with high mesopore-surface area. Such mesoporous microfibers exhibited the efficient catalytic activity for oxygen reduction reaction (ORR) in alkaline solutions with better stability and methanol-tolerance performance. - Graphical abstract: Mesoporous nitrogen-doped carbon microfibers with efficient oxygen electroreduction activity were prepared by thermal conversion of new Mg-biquinoline-based coordination compound microfibers.

Synthesis of boron, nitrogen co-doped porous carbon from asphaltene for high-performance supercapacitors

Science.gov (United States)

Zhou, Ying; Wang, Dao-Long; Wang, Chun-Lei; Jin, Xin-Xin; Qiu, Jie-Shan

2014-08-01

Oxidized asphaltene (OA), a thermosetting material with plenty of functional groups, is synthesized from asphaltene (A) using HNO3/H2SO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon (BNC—OA) is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy (XPS) characterization reveals that the BNC—OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart (BNC—SA) has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC—OA are 1103 m2·g-1 and 0.921 cm3·g-1, respectively. At a current density of 0.1 A·g-1, the specific capacitance of BNC-OA is 335 F·g-1 and the capacitance retention can still reach 83% at 1 A·g-1. The analysis shows that the superior electrochemical performance of the BNC—OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.

A Nanopore-Structured Nitrogen-Doped Biocarbon Electrocatalyst for Oxygen Reduction from Two-Step Carbonization of Lemna minor Biomass

Science.gov (United States)

Guo, Chaozhong; Li, Zhongbin; Niu, Lidan; Liao, Wenli; Sun, Lingtao; Wen, Bixia; Nie, Yunqing; Cheng, Jing; Chen, Changguo

2016-05-01

So far, the development of highly active and stable carbon-based electrocatalysts for oxygen reduction reaction (ORR) to replace commercial Pt/C catalyst is a hot topic. In this study, a new nanoporous nitrogen-doped carbon material was facilely designed by two-step pyrolysis of the renewable Lemna minor enriched in crude protein under a nitrogen atmosphere. Electrochemical measurements show that the onset potential for ORR on this carbon material is around 0.93 V (versus reversible hydrogen electrode), slightly lower than that on the Pt/C catalyst, but its cycling stability is higher compared to the Pt/C catalyst in an alkaline medium. Besides, the ORR at this catalyst approaches to a four-electron transfer pathway. The obtained ORR performance can be basically attributed to the formation of high contents of pyridinic and graphitic nitrogen atoms inside this catalyst. Thus, this work opens up the path in the ORR catalysis for the design of nitrogen-doped carbon materials utilizing aquatic plants as starting precursors.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

Science.gov (United States)

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-01-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g−1 present high specific capacities of the 308 and 200 F g−1 in KOH electrolyte at current densities of 0.1 and 10 A g−1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g−1 at 0.1 A g−1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry. PMID:26472144

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

Science.gov (United States)

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-10-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g-1 present high specific capacities of the 308 and 200 F g-1 in KOH electrolyte at current densities of 0.1 and 10 A g-1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g-1 at 0.1 A g-1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

Effect of carbon and silicon on nitrogen solubility in liquid chromium and iron-chromium alloys

International Nuclear Information System (INIS)

Khyakkinen, V.I.; Bezobrazov, S.V.

1986-01-01

The study is aimed at specifying the role of carbon and silicon in high-chromium melts nitridation processes. It is shown that in high-chromium melts of the Cr-Fe-C system the nitrogen solubility is reduced with the growth of carbon content and in the chromium concentration range of 70-100% at 1873 K and P N 2 =0.1 MPa it is described by the lg[%N] Cr-Fe-C =lg[%N] cr-fe -0.098[%C] equation. While decreasing the temperature the nitrogen solubility in alloys is increased. Silicon essentially decreases the nitrogen solubility in liquid chromium. For the 0-10% silicon concentration range the relation between the equilibrium content of nitrogen and silicon at 1873 K and P N 2 =0.1 MPa is described by the straight line equation [%N] Cr-Si =6.1-0.338 [%Si

Effect of smoke on subcanopy shaded light, canopy temperature, and carbon dioxide uptake in an Amazon rainforest

OpenAIRE

Doughty, C. E.; Flanner, M. G.; Goulden, M. L.

2010-01-01

Daytime Net Ecosystem CO2 uptake (NEE) in an Amazon forest has been shown to increase significantly during smoky periods associated with biomass burning. We investigated whether the increase in CO2 uptake is caused by increased irradiance in the lower canopy, which results from increased above-canopy diffuse light, or by decreased canopy temperature, which results from decreased above-canopy net radiation. We used Sun photometers measuring aerosol optical depth to find nonsmoky (Aerosol Optic...

Selection of Suitable Carbon, Nitrogen and Sulphate Source for the Production of Alkaline Protease by Bacillus licheniformis NCIM-2042

Directory of Open Access Journals (Sweden)

Biswanath BHUNIA

2010-06-01

Full Text Available In this study, selection of suitable carbon, nitrogen and sulphate sources were carried out by one-variable-at-time approach for the production of alkaline protease enzyme by Bacillus licheniformis NCIM-2042. Maximum levels of alkaline protease were found in culture media supplemented with magnesium sulphate, starch and soybean meal as a good sulphate, carbon and nitrogen sources which influenced the maximum yield of this enzyme (137.694.57, 135.231.73 and 134.741.77, respectively in comparison with the other sulphate, carbon and nitrogen sources.

Comparing alternative tree canopy cover estimates derived from digital aerial photography and field-based assessments

Science.gov (United States)

Tracey S. Frescino; Gretchen G. Moisen

2012-01-01

A spatially-explicit representation of live tree canopy cover, such as the National Land Cover Dataset (NLCD) percent tree canopy cover layer, is a valuable tool for many applications, such as defining forest land, delineating wildlife habitat, estimating carbon, and modeling fire risk and behavior. These layers are generated by predictive models wherein their accuracy...

Successive ionization of positive ions of carbon and nitrogen by electron bombardment

International Nuclear Information System (INIS)

Donets, E.D.; Ilyushchenko, V.I.

Experimental studies of deep ionization of heavy ions are described. The applications of such studies in atomic physics, plasma physics and space physics are discussed. Investigations using intersecting ion-electron beams, shifted beams and ion trap sources are described, and data are presented for multi-charged ions of carbon, oxygen and nitrogen. A detailed description of the development of the IEL (electron beam ionizer) source, and the KRION (cryogenic version) source is given, and further data for the multiple ionization of carbon and nitrogen are given for charge states up to C 6+ and N 7+ . The advantages and disadvantages of the KRION source are discussed, and preliminary studies of a new torroidal ion trap source (HIRAC) are presented. (11 figs, 57 refs) (U.S.)

A density functional study of nitrogen adsorption in single-wall carbon nanotubes

International Nuclear Information System (INIS)

Zhu Jie; Wang Yao; Li Wenjun; Wei Fei; Yu Yangxin

2007-01-01

An understanding of the adsorption behaviour of nitrogen in single-wall carbon nanotubes (SWCNTs) is necessary for obtaining information on its pores by nitrogen adsorption manometry. Non-local density functional theory was used to simulate nitrogen adsorption behaviour, including the adsorption isotherms, equilibrium density profiles and potential energy of the nitrogen molecules at 77 K, inside SWCNTs with diameters ranging from 0.696 to 3.001 nm. With increasing diameter, nitrogen adsorption changes from continuous filling in one dimension to a two-stage adsorption that corresponds to monolayer formation followed by multilayer condensation. The average density of the adsorbed nitrogen and the density profiles, especially in small diameter SWCNTs, were used to analyse the adsorbate phase at the saturation pressure. The results indicate that the type of pore filling depends primarily on the ratio of the SWCNT diameter to the adsorbate molecular diameter. The filling of SWCNTs is not a simple capillary condensation process, but is dominated by geometrical limitation

Moisture effects on carbon and nitrogen emission from burning of wildland biomass

Directory of Open Access Journals (Sweden)

L.-W. A. Chen

2010-07-01

Full Text Available Carbon (C and nitrogen (N released from biomass burning have multiple effects on the Earth's biogeochemical cycle, climate change, and ecosystem. These effects depend on the relative abundances of C and N species emitted, which vary with fuel type and combustion conditions. This study systematically investigates the emission characteristics of biomass burning under different fuel moisture contents, through controlled burning experiments with biomass and soil samples collected from a typical alpine forest in North America. Fuel moisture in general lowers combustion efficiency, shortens flaming phase, and introduces prolonged smoldering before ignition. It increases emission factors of incompletely oxidized C and N species, such as carbon monoxide (CO and ammonia (NH₃. Substantial particulate carbon and nitrogen (up to 4 times C in CO and 75% of N in NH₃ were also generated from high-moisture fuels, maily associated with the pre-flame smoldering. This smoldering process emits particles that are larger and contain lower elemental carbon fractions than soot agglomerates commonly observed in flaming smoke. Hydrogen (H/C ratio and optical properties of particulate matter from the high-moisture fuels show their resemblance to plant cellulous and brown carbon, respectively. These findings have implications for modeling biomass burning emissions and impacts.

LBA-ECO ND-11 Litter Decomposition, Carbon, and Nitrogen Dynamics in Agroforestry

Data.gov (United States)

National Aeronautics and Space Administration — This data set contains the results of an experiment to determine litter decomposition and dynamics of carbon and nitrogen release from plant litter of differing...

LBA-ECO ND-11 Litter Decomposition, Carbon, and Nitrogen Dynamics in Agroforestry

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: This data set contains the results of an experiment to determine litter decomposition and dynamics of carbon and nitrogen release from plant litter of...

A Comparison of Mangrove Canopy Height Using Multiple Independent Measurements from Land, Air, and Space

Science.gov (United States)

Lagomasino, David; Fatoyinbo, Temilola; Lee, SeungKuk; Feliciano, Emanuelle; Trettin, Carl; Simard, Marc

2016-01-01

Canopy height is one of the strongest predictors of biomass and carbon in forested ecosystems. Additionally, mangrove ecosystems represent one of the most concentrated carbon reservoirs that are rapidly degrading as a result of deforestation, development, and hydrologic manipulation. Therefore, the accuracy of Canopy Height Models (CHM) over mangrove forest can provide crucial information for monitoring and verification protocols. We compared four CHMs derived from independent remotely sensed imagery and identified potential errors and bias between measurement types. CHMs were derived from three spaceborne datasets; Very-High Resolution (VHR) stereophotogrammetry, TerraSAR-X add-on for Digital Elevation Measurement (DEM), and Shuttle Radar Topography Mission (TanDEM-X), and lidar data which was acquired from an airborne platform. Each dataset exhibited different error characteristics that were related to spatial resolution, sensitivities of the sensors, and reference frames. Canopies over 10 meters were accurately predicted by all CHMs while the distributions of canopy height were best predicted by the VHR CHM. Depending on the guidelines and strategies needed for monitoring and verification activities, coarse resolution CHMs could be used to track canopy height at regional and global scales with finer resolution imagery used to validate and monitor critical areas undergoing rapid changes.

Increased needle nitrogen contents did not improve shoot photosynthetic performance of mature nitrogen-poor Scots pine trees

Directory of Open Access Journals (Sweden)

Lasse Tarvainen

2016-07-01

Full Text Available Numerous studies have shown that temperate and boreal forests are limited by nitrogen (N availability. However, few studies have provided a detailed account of how carbon (C acquisition of such forests reacts to increasing N supply. We combined measurements of needle-scale biochemical photosynthetic capacities and continuous observations of shoot-scale photosynthetic performance from several canopy positions with simple mechanistic modelling to evaluate the photosynthetic responses of mature N-poor boreal Pinus sylvestris to N fertilization. The measurements were carried out in August 2013 on 90-year-old pine trees growing at Rosinedalsheden research site in northern Sweden. In spite of a nearly doubling of needle N content in response to the fertilization, no effect on the long-term shoot-scale C uptake was recorded. This lack of N-effect was due to strong light limitation of photosynthesis in all investigated canopy positions. The effect of greater N availability on needle photosynthetic capacities was also constrained by development of foliar P deficiency following N addition. Thus, P deficiency and accumulation of N in arginine appeared to contribute towards lower shoot-scale nitrogen-use efficiency in the fertilized trees, thereby additionally constraining tree-scale responses to increasing N availability. On the whole our study suggests that the C uptake response of the studied N-poor boreal P. sylvestris stand to enhanced N availability is constrained by the efficiency with which the additional N is utilized. This efficiency, in turn, depends on the ability of the trees to use the greater N availability for additional light capture. For stands that have not reached canopy closure, increase in leaf area following N fertilization would be the most effective way for improving light capture and C uptake while for mature stands an increased leaf area may have a rather limited effect on light capture owing to increased self-shading. This raises

Increased Needle Nitrogen Contents Did Not Improve Shoot Photosynthetic Performance of Mature Nitrogen-Poor Scots Pine Trees.

Science.gov (United States)

Tarvainen, Lasse; Lutz, Martina; Räntfors, Mats; Näsholm, Torgny; Wallin, Göran

2016-01-01

Numerous studies have shown that temperate and boreal forests are limited by nitrogen (N) availability. However, few studies have provided a detailed account of how carbon (C) acquisition of such forests reacts to increasing N supply. We combined measurements of needle-scale biochemical photosynthetic capacities and continuous observations of shoot-scale photosynthetic performance from several canopy positions with simple mechanistic modeling to evaluate the photosynthetic responses of mature N-poor boreal Pinus sylvestris to N fertilization. The measurements were carried out in August 2013 on 90-year-old pine trees growing at Rosinedalsheden research site in northern Sweden. In spite of a nearly doubling of needle N content in response to the fertilization, no effect on the long-term shoot-scale C uptake was recorded. This lack of N-effect was due to strong light limitation of photosynthesis in all investigated canopy positions. The effect of greater N availability on needle photosynthetic capacities was also constrained by development of foliar phosphorus (P) deficiency following N addition. Thus, P deficiency and accumulation of N in arginine appeared to contribute toward lower shoot-scale nitrogen-use efficiency in the fertilized trees, thereby additionally constraining tree-scale responses to increasing N availability. On the whole our study suggests that the C uptake response of the studied N-poor boreal P. sylvestris stand to enhanced N availability is constrained by the efficiency with which the additional N is utilized. This efficiency, in turn, depends on the ability of the trees to use the greater N availability for additional light capture. For stands that have not reached canopy closure, increase in leaf area following N fertilization would be the most effective way for improving light capture and C uptake while for mature stands an increased leaf area may have a rather limited effect on light capture owing to increased self-shading. This raises the

Carbon and nitrogen co-doping self-assembled MoS{sub 2} multilayer films

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaoqin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Xu, Jiao; Chai, Liqiang [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); He, Tengfei [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Yu, Fucheng [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Wang, Peng, E-mail: pengwang@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2017-06-01

Highlights: • Mo–S–C–N composite films were synthesized by using reactive magnetron sputtering. • A self-assembled multilayer structure with periodicity in the nanometer scale was formed in the composite film. • The hardness of Mo–S–C–N film deposited at optimized parameter reaches up to 9.76 GPa. • The wear rate of deposited Mo–S–C–N film both in vacuum and ambient atmosphere decreases dramatically. - Abstract: Mo–S–C–N composite films were prepared using reactive magnetron sputtering of graphite and MoS{sub 2} targets in argon and nitrogen atmospheres. The effects of carbon/nitrogen co-doping and carbon concentration on the composition, microstructure, mechanical and tribological properties of deposited films have been investigated by various characterization techniques. The results show that the deposited films comprise MoS{sub 2} nanocrystalline and amorphous carbon, and the incorporating nitrogen forms Mo-N and C–N chemical bonds. Increasing carbon concentration leads to the increase of sp{sup 2} carbon fraction in the films. Furthermore, the high-resolution transmission electron microscopy reveals that a self-assembled multilayer structure with periodicity in the nanometer scale is formed in the Mo–S–C–N film. Benefiting from the composite and self-assembled multilayer structures, the hardness of Mo–S–C–N film deposited at optimized parameter reaches up to 9.76 GPa, and corresponding friction experiment indicates that this composite films display low friction coefficient and high wear resistance both in vacuum and ambient air conditions.

Modeling effects of hydrological changes on the carbon and nitrogen balance of oak in floodplains.

Science.gov (United States)

Pietsch, Stephan A; Hasenauer, Hubert; Kucera, Jiŕi; Cermák, Jan

2003-08-01

We extended the applicability of the ecosystem model BIOME-BGC to floodplain ecosystems to study effects of hydrological changes on Quercus robur L. stands. The extended model assesses floodplain peculiarities, i.e., seasonal flooding and water infiltration from the groundwater table. Our interest was the tradeoff between (a). maintaining regional applicability with respect to available model input information, (b). incorporating the necessary mechanistic detail and (c). keeping the computational effort at an acceptable level. An evaluation based on observed transpiration, timber volume, soil carbon and soil nitrogen content showed that the extended model produced unbiased results. We also investigated the impact of hydrological changes on our oak stands as a result of the completion of an artificial canal network in 1971, which has stopped regular springtime flooding. A comparison of the 11 years before versus the 11 years after 1971 demonstrated that the hydrological changes affected mainly the annual variation across years in leaf area index (LAI) and soil carbon and nitrogen sequestration, leading to stagnation of carbon and nitrogen stocks, but to an increase in the variance across years. However, carbon sequestration to timber was unaffected and exhibited no significant change in cross-year variation. Finally, we investigated how drawdown of the water table, a general problem in the region, affects modeled ecosystem behavior. We found a further amplification of cross-year LAI fluctuations, but the variance in soil carbon and nitrogen stocks decreased. Volume increment was unaffected, suggesting a stabilization of the ecosystem two decades after implementation of water management measures.

Moderate water stress from regulated deficit irrigation decreases transpiration similarly to net carbon exchange in grapevine canopies

Science.gov (United States)

To determine the effects of timing and extent of regulated deficit irrigation (RDI) on grapevine (Vitis vinifera) canopies, whole-canopy transpiration (TrV) and canopy conductance to water vapor (gc) were calculated from whole-vine gas exchange near key stages of fruit development. The vines were ma...

Effects of climate, CO2 concentration, nitrogen deposition, and stand age changes on the carbon budget of China's forests

Science.gov (United States)

Zhang, C.; Ju, W.; Zhang, F.; Mao, D.; Wang, X.

2017-12-01

Forests play an irreplaceable role in the Earth's terrestrial carbon budget which retard the atmospheric CO2 buildup. Understanding the factors controlling forest carbon budget is critical for reducing uncertainties in projections of future climate. The relative importance of climate, atmospheric CO2 concentration, nitrogen deposition, and stand age changes on carbon budget, however, remains unclear for China's forests. In this study, we quantify individual contribution of these drivers to the trends of forest carbon budget in China from 1901 to 2012 by integrating national datasets, the updated Integrated Terrestrial Ecosystem Carbon Cycle (InTEC) model and factorial simulations. Results showed that the average carbon sink in China's forests from 1982 to 2012 was 186.9 Tg C yr-1 with 68% (127.6 Tg C yr-1) of the sink in living biomass because of the integrated effects of climate, atmospheric CO2 concentration, nitrogen deposition, and stand age factors. Compared with the simulation of all factors combined, the estimated carbon sink during 1901-2012 would be reduced by 41.8 Tg C yr-1 if climate change, atmospheric CO2 concentration and nitrogen deposition factors were omitted, and reduced by 25.0 Tg C yr-1 if stand age factor was omitted. In most decades, these factors increased forest carbon sinks with the largest of 101.3, 62.9, and 44.0 Tg C yr-1 from 2000 to 2012 contributed by stand age, CO2 concentration and nitrogen deposition, respectively. During 1901-2012, climate change, CO2 concentration, nitrogen deposition and stand age contributed -13.3, 21.4, 15.4 and 25.0 Tg C yr-1 to the averaged carbon sink of China's forests, respectively. Our study also showed diverse regional patterns of forest carbon budget related to the importance of driving factors. Stand age effect was the largest in most regions, but the effects of CO2 concentration and nitrogen deposition were dominant in southern China.

Isolation and characterization of a bacterium which utilizes polyester polyurethane as a sole carbon and nitrogen source.

Science.gov (United States)

Nakajima-Kambe, T; Onuma, F; Kimpara, N; Nakahara, T

1995-06-01

Various soil samples were screened for the presence of microorganisms which have the ability to degrade polyurethane compounds. Two strains with good polyurethane degrading activity were isolated. The more active strain was tentatively identified as Comamonas acidovorans. This strain could utilize polyester-type polyurethanes but not the polyether-type polyurethanes as sole carbon and nitrogen sources. Adipic acid and diethylene glycol were probably the main degradation products when polyurethane was supplied as a sole carbon and nitrogen source. When ammonium nitrate was used as nitrogen source, only diethylene glycol was detected after growth on polyurethane.

Chlorophyll meter reading and total nitrogen content applied as ...

African Journals Online (AJOL)

The present study was aimed to assess the relationship between the reading of the chlorophyll meter and the total nitrogen (N) content in the leaf in different parts of the crambe plant, depending on the doses of nitrogen applied to the canopy. Randomized block design in a split plot experimental design was used. The plots ...

QQS orphan gene regulates carbon and nitrogen partitioning across species via NF-YC interactions.

Science.gov (United States)

Li, Ling; Zheng, Wenguang; Zhu, Yanbing; Ye, Huaxun; Tang, Buyun; Arendsee, Zebulun W; Jones, Dallas; Li, Ruoran; Ortiz, Diego; Zhao, Xuefeng; Du, Chuanlong; Nettleton, Dan; Scott, M Paul; Salas-Fernandez, Maria G; Yin, Yanhai; Wurtele, Eve Syrkin

2015-11-24

The allocation of carbon and nitrogen resources to the synthesis of plant proteins, carbohydrates, and lipids is complex and under the control of many genes; much remains to be understood about this process. QQS (Qua-Quine Starch; At3g30720), an orphan gene unique to Arabidopsis thaliana, regulates metabolic processes affecting carbon and nitrogen partitioning among proteins and carbohydrates, modulating leaf and seed composition in Arabidopsis and soybean. Here the universality of QQS function in modulating carbon and nitrogen allocation is exemplified by a series of transgenic experiments. We show that ectopic expression of QQS increases soybean protein independent of the genetic background and original protein content of the cultivar. Furthermore, transgenic QQS expression increases the protein content of maize, a C4 species (a species that uses 4-carbon photosynthesis), and rice, a protein-poor agronomic crop, both highly divergent from Arabidopsis. We determine that QQS protein binds to the transcriptional regulator AtNF-YC4 (Arabidopsis nuclear factor Y, subunit C4). Overexpression of AtNF-YC4 in Arabidopsis mimics the QQS-overexpression phenotype, increasing protein and decreasing starch levels. NF-YC, a component of the NF-Y complex, is conserved across eukaryotes. The NF-YC4 homologs of soybean, rice, and maize also bind to QQS, which provides an explanation of how QQS can act in species where it does not occur endogenously. These findings are, to our knowledge, the first insight into the mechanism of action of QQS in modulating carbon and nitrogen allocation across species. They have major implications for the emergence and function of orphan genes, and identify a nontransgenic strategy for modulating protein levels in crop species, a trait of great agronomic significance.

Investigating Pathways of Nutrient and Energy Flows Through Aquatic Food Webs Using Stable Isotopes of Carbon and Nitrogen

Energy Technology Data Exchange (ETDEWEB)

Hadwen, W. L.; Bunn, S. E. [Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan Campus, Brisbane, Queensland (Australia)

2013-05-15

Carbon and nitrogen stable isotopes can provide valuable insights into pathways of nutrient and energy flows in aquatic ecosystems. Carbon stable isotopes are principally used to trace pathways of organic matter transfer through aquatic food webs, particularly with regard to identifying the dominant sources of nutrition for aquatic biota. Stable isotopes of carbon have been widely used to answer one of the most pressing questions in aquatic food web ecology - to what degree do in-stream (autochthonous) and riparian (allochthonous) sources of energy fuel riverine food webs? In conjunction with carbon stable isotopes, nitrogen stable isotopes have been used to determine the trophic position of consumers and to identify the number of trophic levels in aquatic food webs. More recently, stable nitrogen isotopes have been recommended as indicators of anthropogenic disturbances. Specifically, agricultural land uses and/or sewage effluent discharge have been shown to significantly increase {delta}{sup 15}N signatures in primary producers and higher order consumers in freshwater, estuarine and marine environments. Together, carbon and nitrogen stable isotopes can be used to examine natural food web functions as well as the degree to which human modifications to catchments and aquatic environments can influence aquatic ecosystem function. (author)

Effects of elevated nitrogen deposition on soil microbial biomass carbon in major subtropical forests of southern China

Institute of Scientific and Technical Information of China (English)

Hui WANG; Jiangming MO; Xiankai LU; Jinghua XUE; Jiong LI; Yunting FANG

2009-01-01

The effects of elevated nitrogen deposition on soil microbial biomass carbon (C) and extractable dissolved organic carbon (DOC) in three types of forest of southern China were studied in November, 2004 and June, 2006. Plots were established in a pine forest (PF), a mixed pine and broad-leaved forest (MF) and monsoon evergreen broad-leaved forest (MEBF) in the Dinghushan Nature Reserve. Nitrogen treatments included a control (no N addition), low N (50 kg N/(hm2.a)), medium N (100 kg N/ (hm2. a)) and high N (150 kg N/(hm2. a)). Microbial biomass C and extractable DOC were determined using a chloro-form fumigation-extraction method. Results indicate that microbial biomass C and extractable DOC were higher in June, 2006 than in November, 2004 and higher in the MEBF than in the PF or the MF. The response of soil microbial biomass C and extractable DOC to nitrogen deposition varied depending on the forest type and the level of nitrogen treatment. In the PF or MF forests, no significantly different effects of nitrogen addition were found on soil microbial biomass C and extractable DOC. In the MEBF, however, the soil microbial biomass C generally decreased with increased nitrogen levels and high nitrogen addition significantly reduced soil microbial biomass C. The response of soil extractable DOC to added nitrogen in the MEBF shows the opposite trend to soil microbial biomass C. These results suggest that nitrogen deposition may increase the accumulation of soil organic carbon in the MEBF in the study region.

Identifying the environmental factors that effect within canopy BVOC loss using a multilevel canopy model

Science.gov (United States)

Chan, W. S.; Fuentes, J. D.; Lerdau, M.

2010-12-01

This presentation will provide research findings to evaluate the hypothesis that the loss of biogenic volatile organic compound (BVOC) within plant canopies is dynamic and depends on factors such as plant canopy architecture (height and leaf area distribution), atmospheric turbulence, concentration of oxidants (OH, O3, NO3), and the reactivity of BVOC species. Results will be presented from a new one dimensional, multilevel canopy model that couples algorithms for canopy microclimate, leaf physiology, BVOC emission, turbulent transport, and atmospheric chemistry to investigate the relative importance of factors that impact BVOC loss within a forest canopy. Model sensitivity tests will be presented and discussed to identify factors driving canopy loss. Results show isoprene and monoterpene canopy losses as high as 9 and 18%, respectively, for tall canopies during the daytime. We hypothesize that canopy height and wind speed (i.e. canopy residence time) may be the most important in dictating within-canopy loss. This work will reduce the error in bottom-up flux estimates of BVOCs and ultimately improve parameterizations of BVOC sources in air quality models by accounting for within canopy processes.

Nitrogen deposition may enhance soil carbon storage via change of soil respiration dynamic during a spring freeze-thaw cycle period.

Science.gov (United States)

Yan, Guoyong; Xing, Yajuan; Xu, Lijian; Wang, Jianyu; Meng, Wei; Wang, Qinggui; Yu, Jinghua; Zhang, Zhi; Wang, Zhidong; Jiang, Siling; Liu, Boqi; Han, Shijie

2016-06-30

As crucial terrestrial ecosystems, temperate forests play an important role in global soil carbon dioxide flux, and this process can be sensitive to atmospheric nitrogen deposition. It is often reported that the nitrogen addition induces a change in soil carbon dioxide emission in growing season. However, the important effects of interactions between nitrogen deposition and the freeze-thaw-cycle have never been investigated. Here we show nitrogen deposition delays spikes of soil respiration and weaken soil respiration. We found the nitrogen addition, time and nitrogen addition×time exerted the negative impact on the soil respiration of spring freeze-thaw periods due to delay of spikes and inhibition of soil respiration (p nitrogen), 39% (medium-nitrogen) and 36% (high-nitrogen) compared with the control. And the decrease values of soil respiration under medium- and high-nitrogen treatments during spring freeze-thaw-cycle period in temperate forest would be approximately equivalent to 1% of global annual C emissions. Therefore, we show interactions between nitrogen deposition and freeze-thaw-cycle in temperate forest ecosystems are important to predict global carbon emissions and sequestrations. We anticipate our finding to be a starting point for more sophisticated prediction of soil respirations in temperate forests ecosystems.

Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors

Science.gov (United States)

Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

2017-01-01

Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m2/g and a pore volume 0.366 cm3/g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs. PMID:28074847

Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors.

Science.gov (United States)

Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

2017-01-11

Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m 2 /g and a pore volume 0.366 cm 3 /g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs.

Selection of Suitable Carbon, Nitrogen and Sulphate Source for the Production of Alkaline Protease by Bacillus licheniformis NCIM-2042

Directory of Open Access Journals (Sweden)

Biswanath BHUNIA

2010-06-01

Full Text Available In this study, selection of suitable carbon, nitrogen and sulphate sources were carried out by one-variable-at-time approach for the production of alkaline protease enzyme by Bacillus licheniformis NCIM-2042. Maximum levels of alkaline protease were found in culture media supplemented with magnesium sulphate, starch and soybean meal as a good sulphate, carbon and nitrogen sources which influenced the maximum yield of this enzyme (137.69�4.57, 135.23�1.73 and 134.74�1.77, respectively in comparison with the other sulphate, carbon and nitrogen sources.

High methanol oxidation activity of electrocatalysts supported by directly grown nitrogen-containing carbon nanotubes on carbon cloth

International Nuclear Information System (INIS)

Wang, C.-H.; Shih, H.-C.; Tsai, Y.-T.; Du, H.-Y.; Chen, L.-C.; Chen, K.-H.

2006-01-01